A)
2 Have you ever been to America? Yes, I have. Вместо gone лучше употребить been
3 Have you ever traveled by train? Yes, I have.
4 Have you ever danced hip hop? No, I haven't.
5 Have you ever climbed a tree? Yes, I have.
6 Have you ever won a prize? No, I haven't.
b)
I've traveled by train.
I've never danced hip hop.
I've climbed a tree.
I've never won a prize.