Q15a: Can, say, a 6th-level human re-train their 1st level feat to Able Learner?
Q15b: If, at a higher level, you re-train your first-level feats to Sacred Vow and Vow of Poverty, do you gain all of the bonus exalted feats?
Q15c: Assume an 18 Intelligence at 1st-level and a 22 (w/ +2 item included) Intelligence at 8th level. If, at 9th level, you re-train your first-level feat to be Spell Mastery, how many spells do you memorize with that feat?