1. Has he already known this rule? (General question)
What has he already known? (Special question) Has he already known this or that rule? (Alternative question) Who has already known this rule? (Вопрос к подлежащему, если нужно).
2. Did my brother do his work yesterday? When did my brother do his work?
Did my brother do his work yesterday or last week? Who did his work yesterday? (вопрос к подлежащему, если нужно)
3. Are they waiting their buses on the bus stop now? Where are they waiting their buses now? Are they waiting their buses or trains on the bus stop now? Who is waiting their buses on the bus stop now? (вопрос к подлежащему, если нужно) 1-е предложение в Present Perfect. 2-е Past Simple 3-е Present Continuous