No.sorry.
No you cannot. Only in Ruby,Sapphire,Firered,leafgreen,Emerald,
it is like Pokemon gold,silver,firered,leafgreen,yellow,Sapphire,ruby and emerald versions
Red, Blue, Yellow, Gold, Silver, and Crystal can trade between themselves. Ruby, Sapphire, Emerald, Firered, and Leafgreen can trade between themselves. Games from list 1 cannot connect with list 2.
no
If you trade Pokemon between leafgreen and ruby ruby will have your leafgreen Pokemon and leafgreen will have the ruby Pokemon both in the party they will not be sent to the PC unless you personally walk to the PC and do so.
you must have Pokemon fire red or leafgreen Pokemon emerald or sappire or ruby and Pokemon silver or Pokemon gold then migrate them
Sadly you can't. You can trade From Yellow to : Red, Blue, Green, Gold, Silver and Crystal. From LeafGreen you can trade to : FireRed, Ruby, Saphire and Emerald.
Leafgreen can only trade between firered, ruby, sapphire, emerald, Pokemon colosseum, Pokemon xd gale of darkness, and migrate with diamond, pearl, platinum, heartgold and soulsilver it cannot trade with the original silver.
to get the ruby yes you do
There are none in Pokemon Ruby trade from FireRed or LeafGreen.
Sapphire and Ruby came out before firered and leafgreen but they are compatible with them.
You cannot catch Registeel in Pokemon LeafGreen. This is due to FireRed and LeafGreen being able to trade with Ruby and Sapphire. Pokemon Ruby and Sapphire have the three legendary golem Pokemon including Registeel.