Yes, You Can Teach Charizard To Fly.
Use HM2 to teach charizard fly.
You can teach it anytime you want using HM02.
To teach charizard shadow claw, you must get a heart scale and bring it to the move tutor. Once you do you get to teach it shadow claw.
Episode 136 "Charizard's Burning Ambition". The same episode where Charizard is left at the Charizard training camp.
Go to the battle frontier
Simply use the HM.
The Pokémon that can learn Fly in Yellow are Charizard, Pidgey, Pidgeotto, Pidgeot, Spearow, Fearow, Farfetch'd, Doduo, Dodrio, Aerodactyl, Articuno, Zapdos, Moltres, and, if you use a glitch or cheat to obtain it, Mew. However, it should be noted that none of them learn Fly naturally; you need to use HM02 to teach it to them. Also, as a side note, Charizard is only capable of learning Fly in Yellow, not Red and Blue.
It must be tutored by a special tutor.
Charizard can't learn Cut naturally; it must learn Cut through an HM.
You can't. The only move tutor who teaches Seismic Toss is in FireRed and LeafGreen. Unless you had it there, then migrated it all the way up, your charizard can't learn it. But it shouldn't learn it, Charizard has better moves like Air Slash and Flamethrower. Teach it those. Not having Seismic Toss is not a loss to Charizard. Charizard is actually not that good with his Stealth Rock weakness though.
i don't think it possible
yes but you have to get the TM first