they have really awesome moves
earth, fire, and grass are all super affective to quagsire in Pokemon soul silver
ground types are
Thunder Electric type moves
no.
eruption aquaring
it makes it so that only super affective moves hit
Dragon-type moves are super effective against Dragon-type Pokemon.
no they're the same.
shards can be used to trade with other people. in return, they may teach your Pokemon moves. there are 3 move tutors in Pokemon platinum that will teach your Pokemon moves in exchange for shards in a specific color.
Ice and Fire
The same as in diamond &pearl