Hair is being collected at salons and dog groomers to make the oil absorbing booms.
Donate your hair!
Google it.

They installed a production liner and then cemented. There was obviously a bad cement job! (IMO)
They were going to remove the subsea riser. The drilling mud was being displaced with sea water so the riser could be removed. The mud was heavier than the sea water and holding back any well pressure.
Before displacing the mud in the riser with sea water, a TA(temporary abandonment) cap was installed and tested from the top side. Not tested from below the TA cap. (IMO)