Rings

Q: Are men allowed to wear platinum rings?

Q: Is the wearing of a ring all the time a sunnah since we wear it as jewellery (as adornment)? Did Rasulullah (sallallahu alayhi wasallam) wear it for the same reason or because he needed it to stamp his letters? If it is permissible as a sunnah to wear it all the time, please advise which finger and which hand should one wear the ring? Similarly, how many rings can a male and female wear?  

Q: Please advise on the permissibly of a man wearing an Argentium Sterling Silver ring. Argentium Sterling Silver contains 92.5% of Pure Silver and 7.5% Copper. The Copper is used to strengthen the silver (an alloy).  The weight of the entire ring does not exceed more than 4.374 grams.

Q: What is the criteria a ring has to meet in order for it to be permissible for a man to wear?

Q: Is it permissible for women to wear imitation rings?

Q: Is it permissible for woman to wear rhodium plated rings?

Q: 

1. Is it Sunnah to were a silver ring?

2. If yes to the above question. Must it be pure silver? Should something be inscribed on it? How must it weigh? Which hand and finger to wear it is Sunnah?