Are the delegates won by Cruz/Rubio/Carson/Kasich/Bush allowed to change if their candidate drops out?
Unless the drop-out candidate releases them, they are still bound to that candidate for the 1st convention ballot. After the first ballot, free-for-all rules are in effect for all delegates.
I am not sure how that 8-state majority of delegates will work, however, for delegates pledged to candidates who do not meet that threshold.
Are the delegates won by Cruz/Rubio/Carson/Kasich/Bush allowed to change if their candidate drops out? It varies by state. In general, the delegates belong to the state party and not to the candidate, so the candidate gets little say-so.
I know that Iowa delegate votes can't be changed (even if the candidate drops out) on the first ballot unless only one name is placed in nomination.