How does any of these stablecoins have any value? And does it have to be pegged to something specifically?

Cuz Tether is backed by assets and reserves that aren't on-chain. The US Dollar is backed by the belief that it is worth 1USD but it's propped up by the fact that the US is the strongest military in the world.

If the Fed can print money out of thin air and Tether can too , How does this even make sense?

What is forcing someone from making their own "Tether" and saying its worth 1USD because i said so?