A word that means to depart suddenly is "plump" or "plumped"
all of the sudden, out of nowhere
abruptly, unexpectedly
Abruptly.
a flinch
This could be bolt.
She was driving down the street, but then suddenly, out of nowhere, another car ran a stop light and T-boned her.
Grasp or seize.
Although it has the actual mean of "sudden", the word is abrupt.
No suddenly is a adverb
"Suddenly" is an adverb.
No, but you can make a sentence with the word suddenly. Suddenly it started to rain.
Sprout would be a word for 'to shoot up suddenly'.
Suddenly is an adverb and its comparative is formed by putting the word "more" in front of it.