Have you actually spoken to the garage about any of this? That would absolutely be the first thing to do.

Trying to follow the timeline is a bit of a 'mare but if your suggesting you've had the car back since before Covid kicked off and you've only really got things fixed now, I don't think you're going to have much success based on time alone.
I would have been straight on the phone to them as soon as someone identified no gbox oil.

Sounds like this garage is a joke tho. Mistakes happen, even costly ones, but how you can be missing suspension parts etc on top is mad. Not sure where you are actually based, but if its in the UK get in contact with the DVSA as they'd love to hear the story and would investigate the MOT side of things.

Good luck!