Can Bernoulli or Prandtel predict exactly when the stall occurs.
No. Stall is a viscosity effect. Bernoulli's theorem doesn't have anything to say about viscosity, just speed and pressure outside the boundary layer. Not sure about Prandtl but I don't think he quite got to predicting when and where transition and separation would occur. Both of those are really hard problems. The
Navier–
Stokes equations can do it but that's super computer territory (or a couple of days to solve for a simple case on a high end desktop). Panel codes use a shortcut to estimate the thickness of the BL and where it will transition to turbulent but separation is still not well modeled.
That is, when will the flow become turbulent?
You seem to be confounding turbulence with stall. Stall is separated flow, a turbulent boundary layer resists separation from the surface better than a laminar BL but it also creates a lot more friction drag. When a boundary layer leaves the surface it separates the potential flow of the atmosphere from a small slug of air between itself and the wing. This isolated slug of air is turbulent but on average almost stationary relative to the wing so creates little friction but it's also low pressure so it creates pressure drag (low pressure on aft facing surfaces sucks in the wrong direction).
Here's a video of Prandtl's original experiment showing circulation. The little vortex that gets shed from the trailing edge is what actually starts the circulation by pulling on the upper surface flow with the low pressure at its core thus accelerating the upper surface flow. After that it's a self sustaining feedback cycle. A new starting vortex will be shed every time the plane pitches up.