How v-fold mechanism works - my insights

I made a study into how v-fold mechanism works, especially when a piece on it turns and when it flips.
My popup moving arm card using the inverted v-fold mechanism:
• Pop-up card - Moving A...
Flip up card video by Holly Young:
• How To Make A Flip Up ...
Karen Burniston's tutorial on using the spinner die cut:
• Pop it Ups Rocky Doffs...