Yes
The opposites would be faithful, loyal, steadfast, or true (e.g. a true friend).
· faithful · fanatical · fearless · feisty · fickle · finicky · flawless · forgetful · funny
No true is the opposite to false and Faithful is opposite to unfaithful or disloyal
Unfaithful is the proper opposite of faithful, but dishonest has a similar meaning as unfaithful.
· faithful · fanatical · fearless · feisty · fickle · finicky · flaky · flawless · forgetful · funny
· faithful · fanatical · fearless · feisty · fickle · finicky · flaky · flawless · forgetful
No, "un-" is a prefix that means not. "Faithful" is a word on its own, and adding "un-" to it changes the meaning to the opposite of faithful.
fickle is an adjective
You are so fickle!
The noun form for the adjective fickle is fickleness.
im in a fickle
The opposite of true (factual) is false. It might also be unreal or fictional. The opposite of true (direction) could be skewed or angled. The opposite of true (loyal, steadfast) could be disloyal, unfaithful, or fickle.