When the perfect passive tense stem ends in a vowel or a diphthong, you add the endings of the perfect passive or the pluperfect passive presents no problem but when the perfect passive tense stem ends in a consonant, adding the endings produced awkward clusters of consonants at the juncture between stem and ending.
What is genitive of personal agent:
With most passive verbs, the personal agent (the person by whom the action of the verb is performed) is expressed by the preposition upo + the genitive.
Dative of person agent:
Personal agent is expressed by the dative case without any preposition with the perfect and the pluperfect tenses.
What is the dative of means or instrument?
A thing with which something is done is put in the dative without a preposition.
What is the substantive us of the adjective?
where you take out the noun, and the adjective indicates (based on gender, number, case) "the good man" or "the good woman" by just using the adjective.
Substantive use of the article is where:
the article indicates the person(s), or thing(s) named, and it's case shows its relationship to the rest of the sentence
The articular infinitive is:
The infinitive is a verbal noun, it has tense and voice, it is accompanied by a neuter singular form of the definite article to indicate the infinitive's case. ( An infinitive accompanied by the article). It's used like any other noun