logic true and false questions?

Question

1. different sentences may express the same proposition
2. a valid argument may be unsound
3. the law of non-contradiction asserts that no statement can be both true and false
4. if a term has an intension, then it must have an extension
5. Post hoc ergo propter hoc is a trpe of false cause fallacy

Answer 1

4 is false: the set of all sets that are not members of themselves is an intention without an extension.
1, 2, 3 and 5 are boring.

Answer 2

Item 3 is false.

For example, logically, it cannot be day and night at the same time. This is a question that is relative to the observer's position.

From space and looking at the Earth, the observer can see day and night and at the same time.

Ergo, logic is a flawed way of thinking and perceiving the world.

Answer 3

1. Yes
2. All the time
3. What statement has a possibility of both answers?
4. I don't know.
5.