Look at this page: http://www.serebii.net/pokedex-rs/003.shtml
Charizard: Blast Burn Venusaur: Frenzy Plant Blastoise: Hydro Cannon
Yes your rival will if you choose squirtle, i have a venusaur.
eating
Venusaur Learns:- Growth Lv.43 Sleep Powder Lv.55 Solar Beam Lv.65
It doesn't. Pikachu learns all the moves when you evolve it it will stop learning moves.
Venusaur learns solar beam at level 65 in Red, Green, Blue, Yellow, Gold, Silver, Crystal, Ruby, Sapphire, FireRed, LeafGreen, and Emerald. But Venusaur learns solar beam at level 53 in Diamond, Pearl, and Platinum.
You have to trade it from another game.
Check the related links.
In Pokémon FireRed the moves that Venusaur can learn via level-up are Leech Seed, Leech Seed, Razor Leaf, Poisonpowder, Sleep Powder, Tackle, Growl, Sweet Scent, Growth, Solarbeam, Synthesis, Roar, Toxic, Sunny Day, Bullet Seed, Hidden Power, Hyper Beam, Frustration, Return, Protect, Giga Drain, Earthquake, Double Team, Sludge Bomb, Façade, Secret Power, Attract, Rest, Cut, Strength, Flash, Rock Smash and Tutor moves such as Body Slam, Swords Dance, Double-edge, Substitute and Mimic.
Trade 1 from another player or migrate a bulbasaur, ivysaur or the venusaur from leafgreen or firered
it can learn dragon fang,shadow crunch,water mirror,dragon tail
it doesnt, it can't learn moves cause its evolved with a stone.