Syntax: "All the girls on the block" is a noun phrase acting as the subject. "Knocking at my door" is a present participle phrase describing the action of the subject. "Wanna know" is a colloquial contraction for "want to know," introducing an infinitive clause as the object.
Morphology: "Knocking" is the present participle/gerund form of the verb 'knock,' showing continuous action. "Wanna" is a morphological reduction of "want to," common in informal spoken English.

Syntax: "Is your lover playing on your side?" is a direct question in the present continuous tense. "Said he loves you, but he ain't got time" is a compound sentence. The second clause uses "ain't" as a negative contraction for "has not" or "does not have."
Morphology: "Playing" is the present participle. "Said" is the simple past tense of 'say.' "Ain't" is a non-standard morphological contraction functioning as a negative auxiliary verb.

Syntax: "Take a sip of my secret potion" is an imperative sentence, giving a command. "I'll make you fall in love" is a future tense sentence with "I'll" (I will) as the contraction. "One drop should be enough" uses the modal verb "should" to express expectation. "Boy you belong to me" omits the relative pronoun 'that' (Boy that you belong to me).
Morphology: "Take" is the base form imperative. "I'll" is a contraction of "I will." "Fall" is a bare infinitive after the causative verb "make." "Belong" is the base form verb in a declarative statement.

Syntax: "If you're looking for Mr. Right" is a conditional clause (if-clause) in the present continuous tense. "Need that magic to change him overnight" is the main clause, with the infinitive phrase "to change him overnight" acting as the purpose of the magic.
Morphology: "You're" is a contraction of "you are." "Looking" is the present participle. "Need" is the base form verb in the main clause. "Overnight" is an adverb formed from a noun.