Robotic gas station in China - GIF

[BuffaloJohn]

Who or what opened the door and removed the cap…and how does it get replaced when finished?

Good catch! This is a flap that is opened and a cap that is unscrewed.

Here is an article that directly calls out this type of invention:
https://www.thedrive.com/news/gas-pu...n-nobody-asked

There is an insta video of it in operation and the robot does open the door, unscrew the cap, pick up the nozzle, etc. etc.

There is also an image from a Danish company that invented it.

The sub-heading of the article is fantastic:

Some inventors are so preoccupied with whether they can, they never stop to think if they should.