You cannot without a cheating device such as the Action Replay. Sorry.
No not every pokemon. You can't catch the starter Pokemon and many of the rare pokemon, you have to trade with Diamond. sorry ...
Impossible without cheating.
Not without trading or cheating.
a bunch
Only by trading with a friend.
You cannot get all 3 Starter Pokemon in Pokemon Emerald without trading for the other 2.
You cant without action replay
You can't unless you picked it as starter pokemon.
beat the battle frontier!
In sapphire you cannot get Groundon and Latios without trading or cheating.
its simply not possible