1. Don 't hang up. Hold on, please.

Question

2. Don't hang up. Hang on, plese.
(Can we use 'Hang on' instead of "Hold on' in telephone conversation?)

3. He and I made poses like models.
4. He and I made a pose like models.
(Which one is correct? Do we have to use the plural form 'poses' here?)

5. If he runs fast, he will not be late.
6. If he runs quickly, he will not be late.
(Are both the same and grammatical?)

Answer 1

I'd use #1, #3, #5, and #6.

"Hang on" is too informal, in my opinion. Using the "Hold" button on a phone leads to the "Hold on, please" request.

And yes -- in #4, you need plurals since the subject is plural.