1. No limit on how often you can apply, I thought there was a wait however to get appointments., a lot of Indians are applying for the World Cup.
2. How can you change the approach, the DS 150 questions are pretty objective.
3. Neither?
4. Necessity seems unusual for a sibling, I suppose if that was the case would it not be safest to have it in India?
One thing that could be relevant is on what basis will you be in the US, K1?