Rendolf

The maze thing is right by the Upper Peridot Poke Mart

Yeah you get to her gym by going southeast from Train Town. Also leading with something that has Brick Break is a good idea since she leads with her Sandslash that sets up Aurora Veil.

Yeah Magma and Aqua have different entrances and exits to and from 7th Street, which I was satisfied to learn when I did my second run, since I had wondered why there was a useless building in Lapis and a locked building in 7th the first time around.

A problem with that would be that you aren't able to access the Chrysolia Spring for a pretty long time when you get Surf

You need to interact with the thing in the top left corner of the building that Aster and Eclipse were.

Are you sure that the weather is clear when you're checking?

There's a building in the Beryl Ward that has homeless people in it since the owner left in the chaos. If you go up to the roof at night (the weather might need to be clear too, though I can't quite remember) you should see something happen. Then look around the Peridot Ward (the upper part) and finally check around North Obsidia to finish the quest.

Personally I feel like Mimikyu should be on this list since it doesn't show a location in the dex, the area you go to find it is hard to gain access to, and the place inside there where you get it is a secret I can't imagine someone guessing by themselves easily as well as containing a super dark maze. Also were you really able to complete your dex in just 100+ hours? It took me over 230 to finish it even using web resources.

I'm not really able to, sorry. But I'm sure someone else will be able to help you out.

I would recommend waiting until it reaches level 42 to evolve it since that is when it learns Blizzard which is amazing on Snow Warning Ninetales, especially since the TM for Blizzard is currently unavailable, making that level the only way to learn it.

After you beat Adrienn you get to choose to fund one of 3 projects for the city restoration using your own money, and then you can fund another after beating Titania, and the last after beating Hardy. Fully funding any of the three will grant you access to the Grand Hall's basement. Down one of the hallways to the left you can find a room with a lady who asks you for eggs of all the obtainable starter Pokemon, and offers rewards in return. After you give her 3 starter eggs she'll give you a HP Reset Disc, then another 3 she'll give one for Attack, then Defense, etc. Finally, once you give her all 21 starter Pokemon she gives you both the TM for Shadow Ball and the Garchompite. The problem you might have is that 4 of the starters (Torchic, Snivy, Froakie, and Oshawott/Litten) aren't available at all (unless you picked one of them as your starter) until you finish the final main story mission in Episode 18, right before you're able to get your 17th gym badge. So if you are still a ways from that and still want to go for the Garchompite you would have to ask someone to give you an egg of at least those starters. Also to get the most starters possible, I recommend funding the Azurine Island project, since that one grants you access to Bulbasaur, Chikorita, and Chimchar, while the only other one you get access to from a different project is Oshawott, and that's only if you joined Magma Gang.

Could you not just take the Charizardite X found in your Alpha Sapphire and trade it over to your Y? Or is the problem that you used Pokemon Bank to transfer your Charmander over which wouldn't allow you to have them holding items?

If Greninja does enough damage you might be able to use Water Shuriken's priority to take out Illumise before it can use its Prankster Rain Dance, which would let Growlithe use Flame Burst to change it to a Burning Field, effectively taking away Shelly's advantage. Additionally if you joined the Magma Gang then completing their first quest gets you a Fire Stone to power up your Growlithe more (though if you do this be sure to pay attention to the moves it learns only as Growlithe since Arcanine doesn't get nearly as many, remembering that Flame Burst and Heat Wave are the only ones it learns that change the field). If that strategy doesn't work then you can either try to figure out some variation of it that does, catch some new members (Flying types can be really helpful, especially Taunt-Prankster Murkrow or even just Fake Out Espurr to incapacitate Illumise before it can set rain), or just fight her numerous times to try and brute force it. Good luck!

I would recommend being as thorough as you can and pay attention while playing. Some of your actions can affect how the story plays out, for better or for worse, as well as there being a ton of sidequests and special encounters which can help a lot in battles. Also it's good practice to save your game often, since it can be nice to be able to just go back to before a loss than to have to lose money and such.

You can find one in Ametrine Mountain by using Waterfall after you beat Terra.

Ice Beam itself is not yet available as a TM sadly, and yeah ones of the same caliber hard to come by. So if those are your only criteria then probably pick Torchic.

Technically everybody who starts a game has seen a silver poke ball before, you probably just don't remember. One is actually shown in one of the very first cutscenes, the one where the Meteor grunt who blew up the station is being interrogated.

Don't worry, there's plenty of nature-based stuff to explore once you get outside Reborn City! If you want you can look at the map inside your Pokegear and see what's in the city and what isn't, but if you'd rather not to avoid spoiling it for yourself that's understandable. In regards to the difficulty, you're completely right. This game is extremely challenging. However, allow me to say this: you ain't seen nothing yet. There are a ton of super tough fights that are nothing like what you've seen up to just the first 2 gyms that require strategizing, team swapping, and/or numerous attempts to win. Anyway good luck and have fun, I'm sure you'll have a great time!

And with the Shiny Charm I think its like 3 times more

You could also grind up to level 35 for everybody and that would probably make things easier

It depends on which gang you join. If you join Magma Gang then you get one as a gift from Maxwell after defeating Aqua Gang, but if you join Aqua Gang then one appears in the overworld for you to catch after you defeat Magma Gang. Eventually you get to a point where you can catch them in the wild, but that's not until very far into the game (13 badges).

It seems to me like a slowed down version of Atmosphere- Mirage, but I can't see any track that plays it exactly.

It is Essentials as far as I've seen.

The clown the farthest south and west in Agate Circus is another move relearner. The devs thought ahead when they locked you out of part of the game. Edit: It's not a clown and it's in the southeast, but it's still a move relearner.

The problem with that strategy is that in the Glitch Field, Dark moves do Normal damage. The only thing that Psychic is weak to here is Bug, since the field also makes them immune to Ghost. In that case, the only super effective move you could get with your current would be to reteach your Sandslash Fury Cutter. A strat you might be able to run with that would be to lead with something that has Snow Warning like a Vulpix or Snover or what have you in order to utilize Slush Rush. If that isn't enough then you might have to either try and brute force it or train up something that can take it down.