No, you do not get the interest up front. It gets paid out in intervals just like HBD savings.

But, just because the HBD is locked up for 30 years doesn't mean that you are stuck. You can sell the HBD30 bond at any time. The HBD is locked up, not the value.

With bonds, you can usually calculate or look up the value, which goes down as the expiration date approaches. This is why the issue date is important.

https://www.investopedia.com/terms/b/bond-discount.asp
https://www.investopedia.com/terms/p/premiumbond.asp