Accepting admission offer from more than one institute in United States I'm an international applicant and I'm not very familiar with the routines of admissions in United States. I was wondering if I get admitted from a university and accepting their offer and while trying to get F-1 visa for it, I get another admission from another university, would I be eligible to accept the admission offer of the latter university or not?
You are only allowed to accept admission at one university.  As soon as you do so, you should contact all other universities to which you applied, and tell them you have chosen another school and are withdrawing your application.

If you accept admission at University X, then withdraw it and accept admission at University Y instead in the same year, it's considered unethical behavior, and Y might rescind your admission if they find out.

Most US universities use coordinated acceptance deadlines, so you should know exactly which schools have admitted you before you have to choose one.