1 and 3 are fine. They don't mean the same thing, but they are written well.
2 makes no sense because "will have been" is future perfect, but then "yesterday" throws the meaning into past tense.
1. He will be happy.
2. He will have been happy yesterday.
3. He would have been happy yesterday.
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Are they all grammatical?
Is #2 correct? What is the difference between #2 and #3? Does #2 have stronger possibility than #3? Does #3 mean that he was not happy actually.
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