Yes it can ... this needs to be done at a jewelry shop - pretty standard thing for them to do and it doesn't hurt.
You may want to have that ring checked by a reputable jeweler. It sounds like you have a copper ring plated in white gold and the plating has worn off the underside and is oxidizing from the moisture on your finger. White gold is Regular gold mixed with a white metal like nickel to change its color.
No, but white gold has a natural yellow tint (gold is yellow by nature) most retailers or manufactures plate (rhodium) white gold to give if a whiter appearance. Which will ware off in time.
Most jewellers, especially those with a workshop on their premises, will have a piece of equipment just for this purpose. After the ring has been cut off, give your finger a week or so to get back to normal size before you have your finger measured and the ring made larger.
Yes. U can take any stone and have it replaced in another set
Gold is naturally yellow, but for white gold it is treated with rhodium. Rhodium is a coating that gives it its white color and shine. Sometimes rhodium can wear off of a ring and you will see a yellowish color underneath. But this can be easily fixed by taking the item to a jewelry store to have it re- rhodiumed.
cut it off
It can be Rhodium plated to give it the appearance of white gold. However, over time this plating will wear off and the original yellow gold will begin to show through and you will have to get it re-plated. Contact your local jeweler for more information.
There are a few types of rings that can not be cut off. Titanium and Tungsten Carbide are very difficult to cut off in an emergency situation.
It means that it's cheap, not real gold or that the gold plating is so thin that it's wearing off.
Acetone
White metal used for rings can be either white gold or platinum. White gold is rhodium plated after manufacture to give it a more intense white colour. This plating will wear off over time and will need to be replated with rhodium at your jewellers. On the other hand, platinum retains its colour. Platinum is also harder than gold.
i would see a piercer