Now if you want to use the form 'must have been', it works with the first example:

You must have known meaning. I can't believe i got the final question in the pop quiz wrong. i wouldn't have known the answer either. the first person. But it doesn't work with the second. 3 he must have to know the entry code too.

You must have known jared. 1 he must know the entry code, too. I might have known definition:

1 to express obligation or compulsion: 2 to possess as a characteristic quality or attribute. Then, she must have known.

Ought by all means to. Meaning i guess you have met him. And to this end, i insist that all that.

4 he must have had to know the entry code too. If used with a negative infinitive it indicates obligatory prohibition. [verb] be commanded or requested to.

Most related words/phrases with sentence examples define you must have known that meaning and usage. 2 he must have known the entry code, too. I might have known he would be late.