I once had an accountancy lecturer who would go absolutely apoplectic with rage and frustration, throwing his chalk about, if a student dared answer any of his exceedingly tough questions with, 'It depends'. Likewise, the examiners: the key to passing the mind-bending exams was to take a view and then justify it.
'It depends,' as an answer, is a big fat, 'No Baby, no'.
Try again.
That is very poor procedure. When the correct answer depends on an unknown factor, the rational approach is to establish the unknown factor and then re-evaluate, not to pull a guess out of your nether regions and then defend it.
"Can I legally deduct the cost of my work clothes from my U.S. Federal income tax?" There are IRS rules and precedents about when work clothes are deductible and when they aren't. Until you've established and evaluated certain facts about the particular work and work clothing in question, the only correct answer to that question is "it depends."
The fact is, some vessels heeled 90 degrees will float stably in that attitude (zero righting moment). Others will continue to rotate (negative righting moment) until they invert. Others still will right themselves (positive righting moment). Cargo loading, damage, wind, and waves can all affect any particular case. So the only correct general answer to "what will a ship do after heeling 90 degrees?" without establishing and evaluating more of the relevant facts of the specific case, is "it depends."