Purchasing a bond is effectively just loaning money. I don't know why your distinction would have any relevency

It make a huge difference if the bond fails.

Bob the bank buys a bond from Alice. Criss at the central bank in charge of QE buys if from Bob. Alice goes bankrupt and Bob doesn’t care.

Bob the bank buys a bond from Alice. Criss at the central bank loans Bob money. Alice goes bankrupt and Bob’s bank fails.

Except that Alice here is the government, and in both scenarios Adam The Average Guy loses purchasing power, which is the whole point. The distinction here is purely nitpicking.

Again no, the government accepts loans to private citizens as collateral in these loans.

As a rule these banks just don’t own that many government bonds the returns suck.