You have a error coin and the extra metal on it is called a "Curd". This happens when there is a chip in the die. The value depends on the size of the curd and varies from a few cents to a few dollars.
Check it again. By 1980, all U.S. nickels had mint marks. That said, a 1985 nickel is worth 5 cents.
The U.K. does not issue quarters so I assume you have a Canadian coin. 1985 Canadian quarters are minted from nickel, not silver, and are in general circulation. If that describes what you have it is worth only face value, about 23 cents U.S.
A 1981 Canadian quarter is worth 25 cents in Canada.
In circulated condition, a 1985-P quarter is just worth 25 cents. If uncirculated and graded by NGC/PCGS it might be worth a couple of bucks. If there's any wear or any defects in it, just spend it.
Neither. There's no silver in it and it's not silver plated; it's very nearly pure nickel.
There is one on Ebay for $3.00. The composition of this coin is copper and nickel.
It's a common date coin still in circulation. The coin is face value.
It's still worth one cent in Canada, though they stopped using the penny in 2013. Save up four more and you can trade them in for a nickel.
None. 1985 US nickels are made of copper and nickel. In fact, all U.S. nickels made from 1866 to mid-1942 and from 1946 to the present are all made from that same alloy. From mid-1942 to 1945 nickels did contain a small amount of silver because nickel metal was needed for the war effort. Those "war nickels" are the ONLY ones that have any silver in them.
All 1985 nickels in circulated condition (any wear at all) are worth five cents. Even nickels in absolutely pristine condition are worth only about fifty cents. Only the absolutely one in a billion (literally) coin is worth more, and even then the price tops out at aroung $50USD.
Copper-nickel
twenty-five cents.