And hello yet again, Hela!
In the sentences in your first post there is only one adjective phrase: "very little", in sentence # 3.
An adjective phrase is a construction that has an adjective as its "head" (the most important word. In "very little", "little" is the head -it's an adjective- and the adverb "very" is a premodifier.
In your other sentences there are adjectives but not adjective phrases. For example, in "a beautiful young girl", "beautiful" and "young" are separate adjectives that modify the same noun, but they are not an adjective phrase.
You also ask if a subject could a subject have the form of an adjectival phrase or is it always a nominal. The answer to that is "yes". Certain adjectives can function as heads of noun phrases and so they can be subject of the sentence, complement, object, and object of a preposition. Have a look at these examples. In all of them, the words underlined are adjectives acting as nouns:
Adjective as subject: "The old and sick were helped out of the building."
Adjective as object: "He admires the mystical."
Adjective as subject complement: "The T.V programme you're talking about is The young and the restless".
Adjective as object of a preposition: "He is a big magnet for the undesirable."
In the examples above, determiners (such as the definite article) are part of the adjective phrases, but that is only because the adjectives are "acting" as nouns. On the other hand, in the sentences you posted, the articles are not part of any adjective phrase. They are sort of "independent" modifiers of the nouns.
Miriam