The Cortex M3 processor is part of the power control system, and is not available for general purpose user programming.
There are two PRU real time processors which are available for user programming, usually for real time I-O.
As a beginner, I recommend you start with the latest supplied Debian OS.
There are Android and Ubuntu OS, available. No Windows.
The Pocket Beagle is pinned out for use with "Click Boards". See:
BeagleBone Capes will not mate with the Pocket Beagle connector system.
--- Graham
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