Long bars are identical.
Short bars are identical.
Brown bars are fixed.
All joints are spherical.
The video shows 4 mechanisms during motion.
1. The yellow one in general can not always gives a parallelogram.
2. The blue one in general can not always gives a parallelogram.
3. The green one always gives a variable parallelogram (distance between two long bars is variable).
4. The pink one of one DoF always gives a stable, invariable parallelogram.