Jewellery and Rings

Q: Please let us know whether men can wear white gold? I.e. gold coated with Rhodium. It is look like silver.

Q: Is a belly ring permissible?

Q: We know that one can only use rings made dominantly of gold or silver. Can one use plastic rings?  Can one sell imitation rings which are impermissible to others? Would it make a difference if the customers were muslims or nonmuslims?

Q: Is it permissible to wear a bracelet made of copper for medical treatment? People who have worn this type of bracelet have found it to be beneficial.