Is this chain solid gold or plated?

It is 14k rose gold, a solid alloy, not a plating over base metal. That means the color runs through the metal rather than sitting on the surface.

What length does it adjust to?

It extends from 16 to 18 inches, so it can sit at a choker length or a standard necklace length. The adjustable section lets you set it between those.

Can it hold a pendant?

A small, light pendant suits it. At 1.5 mm the cable links are fine, so a heavy or large pendant can pull and stretch the chain.

What clasp does it use?

A lobster clasp. It is more secure than a spring ring but takes two hands to open and close.

Will the rose gold color match yellow gold jewelry?

Not closely. Rose gold has a pinkish copper tone, so it reads differently next to yellow gold. It pairs more naturally with white gold or other rose gold pieces.