No. The word "vast" is a straightforward adjective, not a participle.
The past participle is had.
Done is the past participle.
The past participle of the word "Find" is the word "Found."
No, the word old is an adjective, not a participle.
The present participle of the word "go" is "going."
The past participle of the word "pick" is "picked".
The present participle for the word 'hit' is 'hitting'.
The past participle of the word "finish" is "finished."
The past participle of the word "touch" is "touched". It is a regular formation.
The past participle of the word 'be' is 'been'. 'They had been running fast for several minutes.'
The word "invited" is the past participle of invite.
The past participle of "swear" is "sworn."