from is the starting point for playback in the sequence, it’s not the length of playback, see the following software update post for details about how the sequencer works
you are right that if from + playback length > sequence end that the end input will cause the playback head to jump to the first step in the playback window. If from + playback length is < than the end of the sequence, then it will jump to the last step in the playback window. It’s debatable whether this is really a bug but I’ll err on the side of logic and change this behaviour next time I get a chance to work on the sequencer.
stop just stops the sequencer, it doesn’t move the play head.
PLen controls the playback window length and from moves the start position of the playback window in the 64-step sequence.
that is what the begin input is used for, while the end input is used to move the playhead to the end of the playback window.