Can a bad engine ruin your cat converter and you knock sensor ?

The mechanic replace my engine but the engine that he put in was no good . I had white smoke clouds coming from the tailpipe and the car would get so hot the oil would burn and evaporate quickly and gas milage was bad . He then pulled his motor out and replaced it with another one and he gave me the car back with a check engine light on the codes are knock sensor and catalytic converter. He reset the code but it came back on . The mechanic is telling me that I need to pay for these repairs but I'm thinking these parts were damaged from his bad engine that he pulled out . Could I be right about this ?

Then what the hell do you have this set for to waste people's time I'm only asking for an opinion . Forget I even asked

Obviously , you think your a superstar . I thought you retired . Stay there

You do no good for anyone so stay retired . "Oh I might get sued if I give out the wrong answer because I don't know the answer " what a joke