1) Is he playing
the piano now? What is he playing now? He is playing the piano now, isn`t he? Is
he playing the piano or guitar now? 2) He was doing (coming???) tasty dinner
yesterday. Was he doing tasty dinner yesterday? What was he doing yesterday? He
was doing tasty dinner yesterday, wasn`t he? Was he doing tasty dinner or
supper yesterday? Здесь во втором с глаголом мне не ясно; не может быть coming, смысла нет)))