An utterance is the perfect or imperfect use of a particular sentence on a particular occasion.
A sentence is an ideal string of words representing a proposition.
A proposition is the underlying sense.
There are 5 utterances for sure. How many sentences and propositions are involved is debatable.
Edit: Sentences are debatable because it depends on how many propositions you believe there are, which depends on which propositions you think each of these utterances is linked ultimately to.