Yes you can migrate your pokemon. This question explains how: http://pokemondb.net/pokebase/877/would-migrate-pokemon-emerald-version-into-game-like-diamond
Not sure exactly what you mean about starters, but if you restart your Sapphire game then yes you will be able to migrate the other starters across.
You will need to get to the point where you can buy PokeBalls and catch pokemon because you must migrate exactly 6 pokemon each time. That takes at least 30 minutes if I remember correctly. You can just catch 6 Zigzagoons or whatever, then migrate 5 of them and your starter.