These are mostly 'zoo sentences', Iba-- they do not exist in real life. Sentence (4), however, is real, and means 'I was supposed to have gone' or 'my going was planned, but I did not go'.
'I have to go' means that you are required (by an outside force) to go, and is not exactly the same as 'I am to go', which means that it is planned for you to go.
Is that clear?
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