you give it a thunder stone, it should evolve
if you mean how to evolve just use a thunder stone can be found in the underground or in random areas of the game
There is no PIKICHU,
You get it in Kanto
No, you cannot give the Pikachu that you started with a Thunderstone and evolve it into Raichu since the game blocks that Pikachu's evolution into Raichu while it is in Pokémon Yellow however you can trade for other Pikachu and they will evolve through the use of a Thunderstone.
It is suppose to evolve at the Level of 20,but if you want it to evolve later it can evolve anything after it is at Level 20.
luck
It will evolve by level. Teddiursa will evolve into a Ursaring at level 30.
They evolve at level 36
It will evolve at level 36.
They evolve on level 40
it evolve on level on 64
if you dont let it evolve at the required level of level 20. itll try to evolve at every level following.