Tension while pedaling, and chain getting stuck pedaling in reverse… any ideas?

Can’t see it in the video but I wonder if the chain isn’t threaded through the pulleys correctly. Guess would be that the chain is on the outside of the pulley cage, not the inside.

Second thought, total guess, is if that chain is directional and it’s on backwards. I’ve never dealt with that so just trying to think of possibilities.

Do the pulleys spin freely with no chain attached? May they are installed incorrectly or too tightly.

the tab on the knuckle of the derailleur that mounts the derailleur to the hanger needs to be rotated back so it rests against the protrusion on the derailleur hanger. Where the 5mm hex head bolt mounts the derailleur to the hanger. Loosen that bolt until it’s almost all the way out, then rotate the derailleur link clockwise about 90 degrees, then tighten the 5mm hex bolt until it’s almost tight, then release the derailleur. It should provide more tension on the chain and operate more normally.

Here’s a picture of what I’m talking about. Notice how your derailleur is just hanging straight down, while the one in the picture is at the 9 o’clock position?

https://wheelsmfg.com/media/wysiwyg/hanger_help/anatomy_sm.jpg

Also, your barrel adjusted has been adjusted too far out and isn’t threaded into the derailleur anymore. Thread the barrel adjuster back into the derailleur and reset your cable tension before adjusting again. While the shift cable is disconnected, make sure your limit screws are properly set.