I'm not sure about the paraphrasing, but in looking for possible ambiguity:
⑴ In the film, Pat was a witch.
the character of Pat is a witch.
We would know that Pat is female because she is termed a 'witch'. If his name was Patrick, he would be termed a warlock. To say 'was a witch' is looking at the movie from your viewpoint having seen the movie. In the actual movie, she is/Pat plays (present tense) a witch. Surely it can't be that Pat could be the name of the actor, and therefore isn't a witch, but plays the part of a witch??
⑵ He promised me to come next week.
The sentence is grammatically incorrect and should be
He promised me he would come next week.
((Otherwise, it would be, "He promised to come next week" and the relative pronoun would have to be omitted))
I can't see anything ambiguous.
⑶ I found something interesting on the Internet.
This is what any native speaker would say. The only other possibility would be, I found something interesting on/about the Internet in a book I'm reading
Please - please - when you find out what seems so glaringly obvious to the person who set this task, please tell us by adding it to this post!
Student or Learner