Yup you will submit cert and transcript for background check process. No grade requirement, this is just to make sure your info is correct and complies with local laws, no criminal history etc.

This background check is sent after you confirm your commencement date with them after they send you the offer. Of course you can tell them you will only get your cert in July or August so they will send you the background check to complete at a later date I suppose.

You'll have to check with your HR point of contact. They won't deny you the offer just because you don't currently have your cert on hand, definitely possible to accept offer first and submit it at a later date once you get it. People have already said plenty of others offered a position have different grad dates like July/ August onwards so they're definitely not anal about it. Of course don't submit it super delayed like in Nov/ Dec la.

No point stressing out here over something out of your control, just make sure you communicate everything clearly with HR once you get offered.