I recently bought my son the leaf Green Pokemon game and he has a couple..

1. Please specify the Pokemon because they do evolve at different levels, all of them. (note levels not ages).

2. There is a mansion in Celedon and when you walk in and talk to an old lady she will give you some tea you try to go through the way to saffron city and the guard will ask for the tea, give him it and you will be able to access Saffron.

3. You will get the poke flute in lavender town go to the place where everyone is praying for Pokemon (note must have silphe scope to see ghosts) then go to the top level defeat the rockets and then talk to Mr. Fuji then you will appear at Mr Fuji house then talk to him again and he will give you poke flute to wake Snorlax.

Charmander, Squirtle and Bulbasaur each evolve at level 16, their next form evolves at level 36, you get the flute by first beating team Rocket in Lavender town where the tower is but first you need the Silph scope, I Think you get to Saffron by beating5 the bridge and meeting Bill. If known of this helps try buying the strategy guide.