Student or Learner
1.Where do you think he will go or would go? (if speak in uncertainty)
2. Whom do you think he has or has he seen ?Could someone show me the correct ways for these?
I am not a teacher.
1. Both are possible. It depends on the context.
2. 'he has' is correct because the question is in 'who do you think?', so there is no inversion. 'Who has he seen?' (without 'do you think') would also be correct.