Not sure but Pikachu evolves by Thunderstone which is a change of form, a Level 2 Pikachu can be evolved into Raichu. An old Pikachu Like Puka may be more childish (immature) than a fully evolved Raichu. There are Pokemon Towers dedicated to dead Pokemon so they can likely die of old age, what a Pokémon's life span is is unknown however.
It's like Cryogonal being able to learn Attract. Some Pokemon moves makes no sense but I agree that Kingdra does not have the bulk for Dragon Tail.
Ah yes Charizard. I have never actually used one although the Solar Power HA looks fun. The Orange Fully evolved Kanto starter needed a boost but couldn't they have done something with Ninetales? Arcanine is a cool tiger like Pokemon but I have never used one preferring its counterpart. That reminds me, I need to Dexnav for a Drought Vulpix. :)
Unova is my favourite region with my favourite Elite Four but Team Plasma are a poor villainous team the part between Marlon and Victory Road is my least favourite part of the game, but Ghetsis is a cool Big Bad.