if you mean the machine on island 1 then that's simple k. just follow these steps.
1:get 60 captured Pokemon on pokedex
2:then go to mt. ember and ther'll be team rocket people fight them and go in tunnel to get ruby.
then talk to oak at his lab and get rainbow pass and unlock islands 4,5,6,7
3fing out how to get sapphire cuz i forgot
get both ruby and sapphire to the man next to the machine
You can get an Electabuzz in LeafGreen by TRADING it form Firered.
You have to fix the network machine in leaf green and get the national dex in emerald
By trading it from FireRed or LeafGreen.
you can't
you need to fix that professors machine on the sevii islands (the seven islands) the ones that you unlock after the league
You can't
Yes, once you fix the machine in One Island in the Leaf Green game. After doing so, you can trade with Hoenn region games.
you cannot catch celebi in Pokemon leafgreen. you can only get it through cheat codes or trading.
Only by trading from LeafGreen and/or FireRed
Only by trading it from Leafgreen/Firered.
It is not possible to get all three starters in Pokemon LeafGreen without trading. This was an intended mechanic to encourage interaction between players.