Not sure if I’m right but: Euphemism is to say one thing in terms of another in a nicer way. So 1 is idiom because it is not a euphemism. Oxymorons are two contradicting ideas used in conjunction, so 2 is allusion. Simile uses like or as, so 3 is a metaphor I don’t think 4 is a euphemism but I don’t know what malapropism is.
