Yes, the present participle of the verb is also an adjective. Example:
The freezing weather is keeping the kids inside.
No, it is not.
Yes.
if you were discribing a noun it could be an adjective.
32.2 degrees Fahrenheit. 0 degrees Celsius.
big is an adjective but to add another adjective you could say extremely big.
No, it is not an adjective. Couple is a noun, or more rarely a verb. Coupled could be an adjective.
No. Although bluish could appear to be modifying white as an adjective, bluish is an adjective and white could be a noun (a color) or adjective (colored).
An adjective for someone who is rich could be wealthy.
One adjective for "signify" could be "meaningful."
no
An adjective for the noun quiver could be violent--a violent quiver.
The adjective for lightning is "lightning." For example, you could say "a lightning storm" or "the lightning bolt."