Pokerus doesn't make levelling up easier.. it just doubles EVs (not experience) gained from battles. The effects don't ever wear off, but you can only spread it for a limited amount of time. The best/fastest way to spread it is to just have the infected pokemon in your party while battling wild pokemon.
Try the original games first, I would say, try Heart Gold and Soul Silver to get some original experience with a new feeling, also try Diamond or pearl..They are pretty good and introduce new pokemon.
Yeah, all my party pokemon have it now XD Plus when I went to the pokemon centre, the nurse explained it to me.
No. Even when a Pokemon is cured, the effect stays. The only thing that goes away is the ability to spread it to other Pokemon. Which is why you keep backups in the PC.
indeed they are, but if you want to find something different in pokemon, well, it is different,,, from what i think, emerald is still the best,,,