I was wondering if any of you know of any competitions or opportunities either online in person that I could do and put on my application. Particularly in the biology, chem, math fields. Things like the ISEF, Biology Olympiad, HarvardMIT math comp etc.
It seems like you already know about a bunch of STEM opportunities - the ones you listed should all be good! From what I know, the USABO (https://www.usabo-trc.org/usabo-2021-calendar-tentative) and the HMMT November tournament (https://www.hmmt.co/rg/info) will both be held online. Why don't you just visit their websites and take a look? Additionally, you could take a look at this list of academic competitions and work from there - https://artofproblemsolving.com/wiki/index.php/Academic_competitions.