[Kanto Starters Team Members Suggestions]

Also, since you have to wait a long time for your mega-charizard, it will be very weak and won't be able to provide sun for your chlorophyll venusaur. Consider getting a ninetales, so your venusaur can sweep more easily. Stealth rocks or spikes would be nice to have also imo

[Kanto Starters Team Members Suggestions]

Not necessarily. I only ever used 6 mons when playing Reborn, cause that's how I always played pokemon. You can totally make it work, but the Kanto starters aren't that strong pre-mega, so stuff like Garchomp isn't a bad idea lol. I feel like Umbreon works on many teams, because it can toxic stall most difficult matchups, which your other teammembers can't deal with.

[Are hidden abilities in the game?]

Hidden abilities are treated as regular abilities in Reborn. This means you can also use ability capsules on your mons to get HAs.