The process really depends upon the style of windows and I cannot tell from your IG photos exactly what you've got. From the pics and the videos (nice job on demo progress, by the way) it does look like there's a metric ass ton of sealant or caulk around the exterior perimeter edges, which may complicate the removal. And really, if they're well sealed you may not want/need to pull them out. But if you do, it's pretty common to have an interior trim ring that screws into the frame, creating a sandwich that holds the outside in place. Or yours may be completely different.
When you get a few more posts, you can start sharing photos here...which will help folks guide you.