You can get a ds/dsi action replay to enter codes. They are about 20-30 dollars and there's tons of codes online. Buy one at Codejunkies.com.
the only way you can do it is to win the next event or use cheatcodes
Cant yet
You don't xD
Unfortunately there are absolutely no Pokemon contests in Heart Gold aside from the PokeAthalon.
you need a gameshark or a action replay, and if you use these, you might not be able to trade, transfer, or battle with other games
yes you can. you can fly back to the indigo plateau and then you can enter the Pokemon leagues again.
the same way you do in diamond and perl
You get safari balls after you enter in safari zone and just in there.
Cheatcodes or luck.
you cant sorry
As soon as you enter Mahogany Town, a man will give you Strength
nm who ever that was you can google it and it is way eaiser ~myla vance