sadly, that method does not exist. that method never existed even in red blue and yellow. its just some made up crap. mew is not under the truck and u cant move the truck either
You cant. You cant.
The Pokemon you can get in fire red and not leaf green are Electabuzz and Scyther.
you cant
You need the 4th badge first to use it.
No it cant.
you cant. only in leaf green you can catch misdreavious.
you cant. at least in leaf green
you cant trade Pokemon diamond pearl with leaf green. You can only do that if you trade Pokemon from leaf green to diamond pearl.
POKEMON LEAF GREEN IS NOT HACKED, SO THERFORE YOU CANT UN-HACK IT.
you cant sorry but u can go from leaf green to diamond
the most probable mistake is that you did not beat the gym.
i am very sorry but you cant get him/her on leaf green.