The cloth of the internal cover of the moonroof of my 1994 850 Volvo has come loose and is hanging. What should I do to fix it. Would gluing it work?

dont do that....
its glued
jast take a flaxible magnet and pull it out

Fix your car right away by clicking the link I attached https://www.reliable-store.com/products/1999-honda-accord-workshop-repair-service-manual-pdf-download-1

moonroof not close

probably the siren module is bad. Moonroof is conected with alarm, and if alarm goes bad, moonroof won-t work. Check out fuses 26 and 28.

there is usually a manual turn hidden somewhere on the inside roof. Find it and turn it with a wrench/screwdriver. Hope this helps :-)

You will have to unplug the siren module and try it. You could try and disconnect the battery for about 20 minutes and then try it again.

You can replace it a couple of ways, my wife broke my side mirror with a paint ball gun, so I just cut a piece of mirror and glued it in the holder. Worked great for years, Till I found a new mirror, and took the real glass out and snapped it in the holder. But you can remove the holder by taking off the plastic cover inside the car behind the mirror, unbolt the holder and hang on to it, it is heavy. You might have to pull the door panel to get the wire disconnected. Then you can either replace it or work on it easily. Hope this helps.

Take it to the dealer, i hand mine fell of when i took it to a carwash and took my car to the dealer right away and they put a new one, glued it together, and it hasn't made a sound nor has it fallen off again.

Housing or just the mirror? Most mirrors are glued to their holders these days.

Find a crashed one near you and but the part. The way the cheapest solution.