you cannot evolve a porygon2 in leafgreen
get the upgrade in the rocket warehouse on Five Island and then trade to another GBA game and then it will evolve. (porygon can be bought at lv. 18 at celadon game corner, and must be holding upgrade to evolve.)
Lv.28
you just evolve it at lv. 40
lv 50
Lv 26
Rhydon at Lv 42.
dragonair evolves on LV 55
Charmelon evolve on leaf green at level 36
Pidgeotto evolves at lv. 36.
Spearow evolves into Fearow at Lv 20.
dragonair evolves at lv 55 but dragonite doesnt evolve
yanma needs to know ancient power to evolve into yanmega. it will learn ancient power at lv 32 and lv it up again and it should evolve ino yanmega.