I recently watched a YouTube tutorial which talks about right usage of past perfect tense. For negative sentences in past perfect, a simple rule to frame sentences is -
Subject + hadn't + main verb in past participle.
Example - He had not learnt music before he became famous.
My question -
Is the rule restricted to "hadn't" coming after the subject? Can we not say something like this -
He did not study music before he became famous.
Is this sentence correct? If it is not, what is the mistake?