I am hoping to book tomorrow, but have some questions about the AS booking procedure.

1. Am I allowed to mix classes on AS (a388 Z+ a345 X)
2. then later change it to a388 Z+ a345 Z, without giving up my a388 Z booking
3. Can the agent book 2 seats and pull the miles from 2 accounts simultaneously
4. Can I add the requisite AS positioning legs, and drop them later if I opt to position differently. (by calling in the drop before departure of course)