Do I have to sand between coats of paint?

Yes, the article did say you could dry the sand overnight. There were 2 options: to bake the sand and to dry it overnight naturally.

Avoid sanding down to the metal under the paint—the sandpaper could scratch the metal.

No. If you put the mug in the dishwasher, there is a high probability the paint will come off.

Two coats of varnish are usually enough for an acrylic painting. Be sure to apply the varnish in thin coats, and wait for each coat to dry before applying another.

You can use polymeric sand, also called joint sand, between your pavers to fill in the cracks.

You're sitting in it! Even if you're just driving for a few minutes, you've got to take the fur coat off. Fur is very unforgiving when it comes to friction...

You would likely need a large or XL depending on the brand's cut, etc. I would suggest trying the clothes on or ordering from a provider who allows free returns.

You can put them in a spare closet, or you can put them in the back of your regular closet during the warmer months so they're not in the way....