Yes, The derailleur is playing no part, there is also rust on the "new chain" if this isn't a Mickey take the op needs to take it to a bike shop to be repaired properly.
Looks like a whole chain has been taken from another bike and thrown over a ring at the front and a ring at the back.
Surprise surprise it didn't work.
Next move is to join a forum and ask them how to fix a slipping chain.
Either that, or it is a bored student in isolation in halls who is taking the Michael.
My money is on the latter and fair play to them. They got three pages out of it.