The aorist signifies nothing as to completeness, but simply presents the action as attained. It states the fact of the action or event without regard to its duration. The Present tense has a generally linear action. The Perfect denotes what has begun in the past and still continues . Thus the present and aorist are the basic tenses of Greek.
Active voice is something the subject of the verb is doing .
Passive voice is something that is being done to the subject of the verb. The infinitive is strictly a verbal noun and not a mood. The Greek dunatoi means strong . By adding an a the word becomes just the opposite, which is adunation meaning weak . All three must be present or it is not Biblical belief.