I forgot versus I had forgot. What is the difference between the two phrases?
"I forgot" is the simple past, expressing an action which took place once.
"I had forgotten" is is the simple past perfect, used to express an action taking place before a certain time in the past. This tense emphasizes what happened, not the duration thereof.
"I had forgot" is generally considered bad grammar, at least in my part of the US, because the correct past participle of "forgot" is "forgotten".
See http://www.ego4u.com/en/cram-up/grammar/tenses for examples of all English tenses.
Kiamlaluno, 'I have forgotten' is the past perfect in British English and never 'I have forgot'. This is simply bad grammar in every other part of the English speaking world except some parts of the US. 'Gotten' is also very bad form in British English, so no sweeping rules please, many of us are not strictly governed by US common usage..