Is it bad/looked down upon if I mention a scholarship(s) that I received from other schools in a letter of continued interest?
Also, what are some things that I must mention in a LOCI?
Yes, don’t do that. They don’t care.
Can I address an omission in the activities section of my commonapp? Like there was a community service activity that I was involved in throughout 9-12th grade but I did not mention this in the commonapp @cavalry
Yes, I would mention that; that is something that can give them a more complete picture of who you are. Good luck with your apps!
Admissions officers are swamped right now and are not looking for more to read. if you write a LOCI it should include any meaningful accomplishments/awards since your application.was completed and a sentence confirming your interest in the school. Keep it short and sweet (a paragraph - not an essay).