Play Sequence using next and prev buttons

Just to confirm... Do you want to switch between several sequences within your pvz file or cycle through steps in a particular sequence?

If former, you can switch between them using 

$scope.view.wdg['model-1']['sequence'] = 'l-Creo 3D - Figure 1.pvi';

or

$scope.view.wdg.playButton.toPlay = { model: modelName, instruction: 'l-Creo 3D - Figure 1.pvi' };

In the latter case, if you just want to cycle through animation steps, you can bind your buttons to the appropriate actions by dragging the buttons' 'Pressed' / 'Click' / 'Pressed' event to the model and selecting appropriate action (Forward / Play / Play All / Reset / Rewind / Stop).

Also, just as a side note, I'd suggest taking a look at the 3D-Guided Service Instructions in the Help Center. It's a great and thorough example showing different Studio capabilities and techniques. It only appeared month or so ago, and not everyone is aware of it's availability.

And the last point... Searching here on Community by "model-1" and "playAll" shows lots of relevant topics with some interesting insights.