Evaluate the similarity between them and classify them into classes from 0-5 as follows:
0 : The two sentences are completely dissimilar.
1 : The two sentences are not equivalent, but are on the same topic.
2 : The two sentences are not equivalent, but share some details.
3 : The two sentences are roughly equivalent, but some important information differs/missing.
4 : The two sentences are mostly equivalent, but some unimportant details differ.
5 : The two sentences are completely equivalent, as they mean the same thing.

Sentence 1: A big turtle is walking. Sentence 2: The tortoise is walking.
4

Sentence 1: Let's let this play out in court. Sentence 2: Nothing is stopping this thing from playing out in court.
4

Sentence 1: If you answer yes to  and no to  you are probably straight. Sentence 2: If you answer no to  but yes to  then you are probably straight.

3