Simply train the Pokemon, nothing is keeping you from training a legit Pokemon to be level 100. If you're too lazy to do that, seek out a Lucky Egg from a Chansey and trade your Pokemon to a different game, this will make you earn 2X the normal exp.
train it
No, it is impossible without the Action Replay.
you could use action replay but if you dont have action replay train at the Pokemon league which will take about a day depending on its level when you start.
to "obtain" 100 lvl pokemon without action replay or any cheats, you have to do it the old fashioned way and train it by battleing other pokemon with it, otherwise there is no other way unless you trade
You can't get Zekrom at level 9 or under without Action Replay.
you cant but u can get a palkia level 47
well you cant even with action replay. in Pokemon blue there is a glitch Pokemon that is mewtwo and its lv225 near that
action replay
911199 HELPME but you can't use this code until you have defeated 20 level 100 Pokemon without an action replay
beat up wild pokemon, gym leaders and trainers
level up or action replay
no