Marcel Felde
You are getting a lot of inaccurate info!!
For example "Beta Range" starts at about +21 deg and finishes at about -9 to -14 deg when the propeller hits the internal reverse stop. There are 3 possible fixed stops on the propeller - Feather - Reverse - and those with the external Zero Pitch Latches for shutdown on float and flying boat aircraft. There is an adjustable hydraulic stop that is controlled by the Power Lever - the Beta Valve - that will change the propeller blade angle progressively from about the + 21 deg to the - 9 Deg..
Read and digest this - it should answer just about everything.
PT6A - Engine Explanation
Regards,
Mx