Retaking year 13

have just received my results and achieved BBC and i am planning to resit.
Mid January my grandma passed away, who i was very close to, and it took a toll on my revision & motivation leading up to my exams in May. Can i use this as extenuating circumstances as a reason for resitting? I am asking because i wasn't diagnosed with depression or anything. Also she didn't pass away during exam period so i don't know if it will be valid reason.
If so, will they ask for evidence (for e.g. death certificates) ?

This can definitely be mentioned as an extenuating circumstance for why your re-sitting because a loss like that would affect your revision for those exams, you don't really need an reason to resit an exam, the extenuating circumstances are usually used so that unis will give you a contextual offer (lower than minimum entry requirments) so you can study there even if your grade doesn't reach the minimum grade requirements, sorry for your loss.

Yes but some universities do not allow resit applicants unless they have extenuating circumstances, so does that mean I can still apply to these unis if I mention my situation?