No, it’s not OK.
If you were a matriculated students and have grades, then you can’t pretend or attest that it didn’t happen. If discovered, you can have your visa revoked and have your diploma rescinded.
You have to certify on your application to US universities that all the information you provided is true. Your teachers from HS presumably know you went to university. Are you going to ask them to lie for you?
The likelihood of an acceptance to Harvard, even if you were a first year are miniscule. Don’t perjure yourself.
No one here will tell you that’s OK.