Can't answer all that!
Saw one at a house I was working on when the cleaning lady was soaking the filters for the vent hood in some type of cleaner solution. When she drain the sink the coating separated from the sink at exactly the same level as the cleaning liquid had been sitting. Have no idea what was used in the soaking solution. The sink had been newly coated about a month before.
A few other jobs have turned up nicks and chips from kids playing in the tubs with toys.
On a few occasions I have also seen water stains from dripping faucets in tubs.
Then there have been a few fish-eyes which is usually a sign of poor cleaning and prepping workmanship on the part of the installer.
I'm afraid I would be scared away from those products.
All of those jobs were done by professional companies and not the DIY crap sold at the big box stores.