Need help in choosing the university for Masters in computer science

I need a help in taking a decision.I got admit from 3 universities in computer science they are cal poly pomona,UT Arli

I'm planning to go US for this spring 2022.I haven't taken any test so far. IELTS slots are filled till November. Looking for GRE waiver universities. I'm planning to take Duolingo test in next 5 days.

with only duolingo score will I make it to US for this spring 2022. If I start applying for colleges from Sept 15 onward

Do Professional LOR’s require any stamp from the company?

Do we need to get the lor sealed / stamped or is it not required and can we submit a pdf?

What are my chances of getting in to MS CS fall 23 at USC?

Gpa : 8.8Gre : 328, 169Q, 159VIelts: 82 projects and 2 years work experience.My main concern is that my bachelors