A question was closed after 12 hours and deleted after 10 hours. I searched on meta to know if there is a grace period for re-open and some post mentioned it was 2 days. So can someone confirm if it is 10 hours or 2 days.
The two day "grace period" you talk about primarily affects the owner of the question: they can't delete their own closed questions immediately, and have to wait 48h to do so.
Users with a reputation between 10k and 20k cannot vote to delete questions immediately either, they can only do so for questions that have been closed for 48h, a bit like the owner of the question.
Moderators can close and delete questions immediately and single-handedly.