Sam, no the CAPS does not trigger the ELT
I assume the door could be opened with ease once a CAPS pull has happened, in this particular case I am assuming no CAPS as the plane disintegrated suggesting extreme high impact, these are very strong aircraft and takes considerable G forces to break them up.
BTW my preferred ditching option over water would be CAPS giving more time to prepare for hopefully a safe exit into the dingy and make May Day calls etc.