Available for or in all of January or during

I have written a few sentences below.

(1) I will not be available to work as a substitute in all of January.

(2) I will not be available to work as a substitute for all of January.

(3) I will not be available to work as a substitute during the entire month of January.

I made up the sentences myself. May I ask two questions?

(A) Which preposition is correct: in or for?

(B) Which sentence sounds natural to native speakers?

Thanks for your help.