I have booked an OW Explorer ticket departing KIX, going like KIX-HKG-MAD-ORD-DEN-(Several USA points)-JFK-HND. I would like to know if the following changes are possible:

1. On the return, can I choose to go JFK-HKG, and then stopover, then HKG-KUL-HND? That is, can I go through HKG twice?
2. Within the USA, can I go through one airport multiple times? For example, after DEN, can I do DEN-DFW-BOS-DFW-JFK-HND?

Thanks!