Depends how you look at it...chain ususaly lasts longer but its very expenisve to change . With belt there are set intervals .
Common issue with chain is rattle on startup as usualy one of the tensioners fails... and is it for a lifetime , not sure
Yes .over time this will cause rust
Tipical a6 c6 issue. Check the cap on the heqdlight if its in place and corectly installed. Sometimes on of the clips breaks ... also there is a rubber seal around the cap
Some ppl repotred that drilling 2-3 small hols on the bottom of the headlight helps with air circulation