sneaked. snuk is a bit more "folksy"
The past participle of "sneak" is "snuck" in American English. In British English, the past participle can also be "sneaked."
Formed is the past participle of form.
Sneaked and snuck are both accepted in standard English.
The past participle is laughed.
The past participle is given.
The past participle is worn.
The past participle is relied.
The past form of "am" is "was" and the past participle is "been."
Present participle - developing. Simple past - developed. Past participle - developed.
Sent is the past participle of send.
Introduced is the past participle of introduce.
Past participle: slain or slayed Past form: slew or slayed