1. is usually a frequency adverb, which means "often" and "habit", which means following the routine, and its regularity is about 90%.

2. Usually, it can only be used as an adverbial, which can be placed before the notional verb, after the copula verb, auxiliary verb or modal verb, or at the beginning or end of a sentence to express emphasis. When used in negative sentences, it is mainly located between the notional verb and the copula verb, auxiliary verb or modal verb.

Usually it can also be placed in front of a negative sentence, indicating that something usually won't happen.

Fourth, the usage of exception is different from usual. Exception can only be used to modify adjectives or another adverb, not verbs. He likes chocolate unusually. He likes chocolate very much. I see, your homework is very good. It turns out that you have done your homework very well.