What happened prior to the BB was ongoing.
Still ongoing to day.
And, so, detectable.

How can we be sure that something happened before the BB?

Let’s try to understand what definition is.
Definition is equal and opposite relativity.
What defines dimensions of space. Equal and opposite relativity.
Plus dimension relative to negative dimensions.
Equilibrium. Balance. Definition.
Before equilibrium.
Non.
Ongoing.
No time.
No position.
No relativity.
No definition.
Dimensions in Non-equilibrium fluctuate.
interact.
Fluctuations phase.
Gravitate.

If we Untangle dimensions of space see before the BB what would we ‘see’?
Can we detect non-equilibrium Ds? No.
Could we detect fluctuations phase. Yes.
Would we see what happened before the BB? Yes.