Question

1. What is he like?
- He is strong and tall.
- He is active and generous.

2. What does he look like?
- He is reserved and friendly.
- He is average height.

(Are they all grammatical? What is the difference between question 1 and Question 2?)

Answer 1

Question 1 seems to be asking more about his personality and character traits. Question 2 is asking about what he looks like ... height, coloring, etc.

Both of the answers for #1 are fine, but only the second answer for #2 is correct.

Answer 2

Thank you for your help...

3. What is he like?
- He is short and long hair.

Then is this answer acceptable as well?

Answer 3

These sentences would work with this question:

What is he like?

He is friendly and outgoing.
He is a very good student and spends lots of time in the library.
He is a very good athlete.

In other words, the answers need to focus on his personality and character, not his looks.

In re-reading my reply above, I see the error I made. Here's a correct explanation for you: Of the first two questions you posted, the first one elicits answers about his character, and the second one is expecting answers about his physical appearance.