Peptides
The antibody.
No, because each antigen has a specific structure that makes its shape complementary to just one other antigen (just like with enzymes, which are specfic to one substrate). Consequently, your body...
epitopes on the antigen while the paratopes on the antibody
It depends on the antibody. There are several types of antibodies. Antibodies are alse called immunoglobins. I hope this helps:)