graduating/college admission/osap questions

Hi so I just have a few questions about graduating with ilc, the process of it all and the timeline for accepting college offers and applying for OSAP.

For some context: I am currently working through 4 grade 12 courses which I hope to finish by mid April. After these I will take 5 more gr12 courses which I hope to finish by late July/ early August. I have already applied and received offers from 4 college programs, but I am still waiting on my top 1 (I've been waitlisted). I'll divide my questions below

1. When do offers stop coming out for waitlisted programs, specifically vet tech at Seneca if that helps answer my question.
2. I know I have to accept an offer by May 1st and deposit the $200 before June 1st. when during this time would I apply for OSAP?
3. When do colleges prefer applicants to have their OSSD completed by? and how long does ILC usually take to finalize the diploma. I know I also have to request a diploma assessment, when if it recommended to request it by.

That is all for now, I may or may not add questions below. Thank you!