About the move rules...

So as long as the move can be learned by that Pokemon, it's OK, right?
I was thinking if whether or not it would be OK to have Pokemon like a Charizard with Skull Bash or a Snorlax with Fissure as the only way you can get them to know these moves is through special means.
(Skull bash and Fissure are 1st gen TMs, and Shadow Snorlax, when purified, learns Fissure.)
This is still OK, right?

It should be up to date; if a Charizard can't learn skull bash in the most recent generations, it can't be used.
And if your Snorlax was a shadow pokemon, then it can use fissure. If not, then it can't.

Oh, Ok. Thank you.