Equipt is an alternative spelling for the word "equipped"
"Equipped" is the simple past tense and past participle of the verb "equip"
The past participle is equipped. Equipt is also accepted.
The present participle is equipping.
Quite often the simple past tense and past participle of verbs were spelled until the 20th century with a "-t" instead of an "-ed" thus "burnt" became "burned", "equipt" became "equipped", etc.
The past participle of "am not" is "have not been."
The past participle of "do" is "done." The past participle of "have" is "had."
The past tense of "have" is "had," and the past participle is also "had."
The past and past participle for "buy" is "bought."
Being is the present participle. The past participle is been.
The past participle is thought.
Eating is the present participle; eaten is the past participle.
"Did" is the past and "done" is the past participle.
The past participle is had.