There is a series of ST16S Unlock guidelines. One for HPlus, one for H520, one for H3.
If you know which APP is currently on the controller, you can use that one. Otherwise, just use the one for the model you want to wind up with anyway. The Update.zip file is the same for all three. It is a "poison apple" that chokes the controller to death and makes it come back to life as an android recovery screen.
The recovery screen has a factory reset option.

After the factory reset, you load the firmware for the controller you want it to be. The three different packages have the model specific reload files included.
ST16S series Unlock Guidelines
None of these guidelines will work for the original Typhoon H ST16. See "
Way To Fix Drones project" Table of Contents if you need to unlock an original ST16.