Idiom Usage:
This idiom is often used with the verb "to go" as in:
- You need to go back to square one.
- You have to go back to square one.
- You should go back to square one.
- Do you want to go back to square one?
With the verb "to go", you can
only use "to".
With the verb "to be", you can use "to" or "at":
- You are back to square one.
- You are back at square one.
The meaning is the same.