Misc: What's the only element capable of tarnishing and damaging gold?

Questions

What was the name of Arnold's fish on Different Strokes??

On Three's Company,what was Jack's retaurant that he opened and was head chef ??

On Three's Company,what's the first name of Mr. Furley's (landlord) tight wad brother who owned the building??

On Three's Company,what city did the trio live in??

On Three's Company,what is the name "Chrissy" is short for??