Should you use "in" on any time duration?

[Aikuzo3]

The class will finish in a minute
The class will finish in an hour.
I can move my things in a day.
I have to wait for that mail in a week.
I will have to study those equipment in a month (btw, is "those equipment" gramatically correct as well?)

Am I getting things right?

[Rover_KE]

Only 1, 2 and 3 (if you had numbered them) are correct.

'Those equipment' is ungrammatical.


Rover

[Nehushtan]

I have to wait for that mail in a week.

This should be “I have to wait for that mail for a week” or “I have to wait a week for that mail”.

I will have to study those equipment in a month

This is ambiguous. Do you mean “I will have to study the equipment in a month’s time (= a month from now)”, or “I will have to take a month to study the equipment”? (Note that “equipment” is singular.)