I am seeking a chain that i will not take off. how strong is the clasp for such use? (my last one i wore for 7years and it just broke) thanks

This isn't real silver and the chain isn't durable. I bought it for a friend , he wore it everyday until a month ago the clasp broke off. Wouldn't recommend it.

Can the plain side be engraved without ruining the non tarnish coating

My apologies. I'm not sure. I haven't tried that.

how is the closure on the chain? Is it one of those larger lobster claw clasps?? Or is it one of those delicate little circle clasps?

This is my husband's cross and he wears it all the time, even in the shower. He has had it several months and it has held up very well. It has a smaller circle clasp.

Will it turn colors if wet?

No it won't initially. I have had mine for 4 weeks and worn it in the shower probably 4-5 times a week. If it does start to turn color, you can always go to the jewelry section in Walmart and buy some sterling silver jewelry cleaner which will clean it all up and keep it looking shiny!