Hello, SFgirl-- and welcome to English Forums. ' -- That's the basic rule, yes, but like is becoming more flexible and is accepted by many, especially informally, in the second function. I don't understand your second rule about 'subjects' and 'actions'; I suspect it is the same as the first rule, since a prepositional phrase contains just an object noun ( He looks like an idiot ) while a subordinate clause contains a verb- which usually expresses some sort of action as well ( I'll treat him as I would treat anyone ).
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