Are we allowed to leave out certain SAT/ACT scores when self-reporting, or do we have to include every single test?

The best answer is to verify with each college you are applying to.

I opted to send all scores to a certain amount of colleges.

No colleges or universities to my knowledge require applicants to submit any ACT or SAT scores this cycle.

Therefore logically, no colleges should require any applicants to submit all ACT scores or all SAT scores, or both sets of test scores BUT that is not reality.

Some schools want to see everything, even in this 2020-21 test-optional cycle so it's a catch 22.

And some colleges "highly recommend" or "highly encourage" you to submit your complete set of scores to them., which means please oblige us if you don't mind. This admissions cycle, I'm going to send all my ACT/SAT scores to Stanford, Dartmouth, Yale, and Brown.

I found this list on "Prepscholar "for colleges that want all your test scores.

https://blog.prepscholar.com/colleges-requiring-all-sat-scores-complete-list

CollegeVine's list looks like this:

https://blog.collegevine.com/which-colleges-require-all-sat-scores-sent/

Carnegie Mellon University | CMU

Clarkson University

Coker College

College of Charleston

College of St. Benedict | CSB

Duquesne University

East Georgia State College | EGSC

Elon University

Georgetown University

Gonzaga University

Johns Hopkins University | JHU

Loyola University New Orleans

Ohio Wesleyan University

Seattle University

Shorter University

University of California, Berkeley | UC Berkeley

University of South Carolina | USC

Yale University

Also, keep in mind that many schools do not superscore the SAT or ACT, or some schools superscore the SAT but not the ACT. (e.g. Harvard)

https://www.compassprep.com/superscore-and-score-choice/

Good luck