If the last date for accepting admission at a university is before you hear back from other choices

Hey I had a doubt. The last date for accepting admission at CU boulder is 29 April but I m yet to hear back from purdue and Maryland. Purdue I heard wont roll out decisions until May. So if I accept the admission at CU n later leave it for purdue, can it be done? What are the consequences in terms of visa, i-20 or any penalties?