It is possible (by spontaneous mutation, for example) but unlikely.
yes
Yes, they can.
Yes.
No, if both parents are type O, the child must be type O. However, since one parent is positive and the other is negative, the child could be either positive or negative.
for sure
Yes they can.
No, an O-group parent cannot have an AB-group child at all.
If the mother has type negative blood, and the father and child have type positive blood, the mother's blood may begin to attack the child's.
No. If both parents are Rh+, they can only pass on Rh+.
No. If both parents are Rh+, they can only pass on Rh+.
Yes - if both are heterozygotic for RH factor.
No, an O-group parent cannot have an AB-group child at all.