A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
The PowerPoint part of your question is simple enough. Make the slides for each section automatically transition to the next, except for the last slide in the section. On this slide, make the transition manual. Then add 2 hyperlinks, one to go to the next section and the other to take you back to the first slide in the section.
I'm not clear why you then need to duplicate this in a deck with video versions of the same material. But place each video on its own slide,,set them to play automatically, and add 2 hyperlinks, one to re-trigger the movie and another to go to the next slide.