Yes, 'these' can function as a demonstrative adjective, as well as a demonstrative pronoun. Examples where it is an adjective include:These bananas are very ripe.
I made these curtains last year.
if you were discribing a noun it could be an adjective.
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).
One adjective for "signify" could be "meaningful."
An adjective for someone who is rich could be wealthy.
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."
No, the word snake could be a noun or a verb, but not an adjective. And second of all, what's with the grammar? A adjective?
Yes, peaceful is an adjective. The noun form could be peace or peacefulness.
No, switch can be a verb or a noun. Adjective forms could be switched or switchable.