The correct answers are Have you been playing your drums again? and What have you been doing in the garage all afternoon?

To form a question in the Present Perfect Continuous, invert the subject and the first auxiliary verb: Have/Has + Subject + been + verb-ing?

"How long have you been practiced" is incorrect because it uses the past participle (practiced) instead of the present participle (practicing).

"Has you been making" is incorrect because the pronoun you always takes the plural auxiliary verb have, never has.