Rendolf

If you got the Whismur encounter early on (or you grabbed an egg before you wonder traded) you can breed one and hatch the egg in 7th Street and it'll count once you evolve it to Loudred. Those are the only ways to encounter the Whismur line though, so if you have neither then you will need a trade.

During day time and clear (maybe sunny too) weather, if you look in the Lower Peridot Ward you'll find the hiker you got a house for in the lower right park area and he gives you the other choice item from your gang leader.

Steel for me

I don't think this is the right place for it, but assuming you mean Reborn this should help: https://pokemon-reborn.fandom.com/wiki/Membership_Card

I'm always a fan of Empoleon: fun typing, not overly op, not super fast but good bulk to make up for it, not to mention an awesome design. You can also teach it pretty much any HM you need (minus Flash and Fly) and in Reborn you can get rid of them whenever you want like TMs

Technically you can make it back to the city from there, but yeah it is a long trek. Vanhanen Castle -> Vanhanen Labyrinth -> Route 1 -> S. Aventurine Woods -> Tanzan Mountain -> Chrysolia Region -> Underground Railnet -> C. Obsidia Ward

Man you were able to beat Charlotte on your second try in your first playthrough? She is quite possibly the hardest gym leader out of all of them so good job for that

It's hard to say. I'm sure at least some fraction of them will be coming back but who knows. Depending on which routes you took there are also some other people in sorta similar scenarios, so we'll see.

Should be a visible Poke Ball. If you can't find that then the other way is on the 11th floor of the Department Store, but you don't get that until towards the end of Episode 18.

You can get one on Route 2, past the Celestinine Cascade.

Steel was my first too and I had a pretty easy time with it (Shade was a pain though, even with my Pawniard god roll)

Good to hear!

Apparently if you hatch an Iggylbuff egg in the (upper) Peridot Ward then you can give that to her I think (Or at least I've heard that sort of thing about other returned Pokemon so I'd assume it works here, too).

One thing you'll definitely want is a Ninetales for its Drought ability, so be sure to find all the police officers and hope you get lucky with a Vulpix. If you don't get super lucky with a Vulpix then be sure to catch a Stunfisk once you get to Apophyll Beach, you'll need it for later. Torkoal also gets Drought so you can get one of those too, but it isn't available until much later in the game.

That's weird, I'm not sure why that would be the case. It should get it according to Bulbapedia.

Obsidia Park, 20% chance any time of day

Sure thing

Well actually when I say Thunderbolt is available I mean that you can get it just before the last gym battle. So you might have to survive on Discharge for most of the game haha

Nope, sorry. Thunderbolt is available eventually, but since you specify Galvantula I'm guessing you intended it to work with Compound Eyes...

You get Kantonian Vulpix from a trade for a Stunfisk and you can't go catch one once you gain access to the trade.

The no over leveling rule isn't really necessary because in Reborn if you get higher than the level cap your Pokémon won't listen to you. But if you want my honest opinion, the game is already hard enough as it is the first time through so Nuzlocking it is kind of overkill. You're pretty much guaranteed to lose battles even without these restrictions in place, and having to restart the entire game on top of that would just be a total pain. That's just my two cents so you're still welcome to do whatever you want.

I think that the ability to check your relationship points like this is a feature of a mod, I'm pretty sure there isn't any way to normally check them in game.

Some tips for each of your members. Politoed: Seems pretty good, although having both Toxic and Perish Song feels redundant. You also might want to train Special Defense rather than Defense, but that's up to you. Mantine: As was said above, Mantine doesn't get Hurricane in Gen 7 and Ice Beam as a TM is not yet available in Reborn, so you'll need to swap out those moves. One thing I definitely recommend you have on it is Roost. Mantine got Roost in Gen 7 and it was a godsend for it, pretty much if you're running Mantine you're running Roost too. Also you get Leftovers pretty late so you need a placeholder item until then (remember to not sell your Balm Mushroom). Magnezone: Again as said above the TMs for Volt Switch and Thunder aren't available yet. Unfortunately that means that you won't be able to utilize the rain for your Magnezone much. Additionally you don't get access to Magnemite/Magneton until fairly late in the game and you aren't able to evolve to Magnezone until even later. If those don't discourage you, then I would recommend against using Zap Cannon since it's super unreliable (you might have meant to say Flash Cannon which is a good choice) and Sunny Day is not great on Magnezone since you'll take even more Fire damage. For replacements I would definitely say use Flash Cannon as it's a really solid special Steel STAB and probably Discharge (maybe replace with Thunderbolt when you get the TM, but that's super late. actually looking at the Rainbow Field effects probably keep Discharge since that would be a 60% chance to paralyze). The other two moves could be pretty much anything you want, if you're running sun on something else then Rainbow Field moves could be useful as was recommended. Steelix: Steel Roller doesn't exist in Gen 7 and you can't get the TM for Earthquake yet. For a Steel move you'll probably want Gyro Ball since Steelix is pretty dang slow. Nothing in the game is really a good replacement for Earthquake, but the best you can do is probably Stomping Tantrum, and maybe have Dig/Bulldoze or an elemental fang move until you get the tutor. Infernape: U-Turn and Swords Dance unavailable. If you still want to do physical be aware that the tutor for Fire Punch isn't available until pretty late, so you'll need alternate Fire STAB until then (Flare Blitz is powerful, but it's learned at a high level, though you'll definitely be there before Fire Punch). I'd definitely recommend Close Combat since it's super strong and Mach Punch isn't really enough Fighting coverage. Keep Mach Punch though, and for your last move I would say either Thunder Punch or Bulk Up, both available at/after you can get Fire Punch, or you could use it as your sun setter. (Special is an option too: Nasty Plot, Fire Pledge/Flamethrower, Focus Blast, Solar Beam or something) Wigglytuff: It's alright. Dazzling Gleam, Hyper Beam, and Heal Bell are all unavailable until pretty late and Copycat is only learnable by Igglybuff at level 11. I would recommend Hyper Voice over Hyper Beam since it's still pretty strong but doesn't require recharge plus it goes through Substitutes, and it's available slightly before you get Hyper Beam. You could run Sunny Day and Flamethrower as was suggested, but even so Wigglytuff isn't amazing and you might be better off swapping it for something with Drought (Torkoal isn't available until pretty late, so you might be better off with Ninetales. You have a 1/18 chance to get a Kantonian Vulpix before the 3rd gym, otherwise you can get it a while later; just be sure to catch a Stunfisk when you get to Apophyll Beach. Also remember to wait until level 42 to evolve it if you want Fire Blast, since the only good attack that Ninetales learns by level up is Flamethrower). The reason why this would be called a Rainbow team is that in Reborn if you set up Rain and Sun at the same time it will change the field into a Rainbow Field which has all kinds of cool effects, all of which are listed here: https://pokemon-reborn.fandom.com/wiki/Rainbow_Field But that's pretty much it. Sorry it was a bit long, I went into progressively more detail as I went along. Anyway have fun!

My guess is that it would either stop you from progressing or do nothing at all, depending on how the devs coded it.

Voltorb Flip is the way to go imo. Once you figure out how everything works you can get a lot of them pretty quickly.