What if Harvard found my whole application great (essay, GPA, recommendations, achievements…) and wants to admit me, but then they see I have an SAT of 1900? 
will they simply reject me?
Honestly unless you have some killer achievement that blows them completely away yeah probably…
Since you’ve already posted in another thread. I’m gonna tell you about the admission process per se. First round, they look at academics (they would prioritize transcript first then standardized test scores), then ECs, PS, etc. Having a 1900 SAT is definitely not really appealing but it depends on whether they would account the situation that you are in.
What if Harvard found three people’s whole application great (essay, GPA, recommendations, achievements…) and wanted to admit them, but then they one has an SAT of 1900 and the other two have 2300 and 2360?
What would you do if you were the Harvard admissions officer? THey have plenty of all three – but a limited number of beds. THus the 5% admit rate.
Indeed, it’s HIGHLY likely that all three are rejected.
It’s not that you’re not qualified. MOST applicants are qualified. But those are simply the numbers