My son received some bakugan(armored alliance) and i have some questions about the rules. I suppose someone around here will know the rules

.
1) each player puts his 6 cores on the field. As i understand it, those 6 cores should match the types of at least one of the 3 bakugan in his team, right?
2) I roll a bakugan. On his character card the shield and the green fist, but it opens on the red fist. What is the result of opening on the "wrong type" of core?
3)we've got 8 little ones from the armored alliance serie, and one big tennisball size battle planet thing. Are those compatible or not?