Who created the department of Diwan-i-Arz in Delhi Sultanate?

The department of 'Diwan-i-Amir-Kohi' dealt with which of the following during Sultanate period?

The Sultan of Delhi who was very concerned about charity and alms and established a department called ‘Diwan-i-Khairat’ for it, was:

Who became the Sultan of Delhi after the death of Balban?

Who among the following established Delhi as the capital of Sultanate?

Who was the first Sultan of Delhi to participate in the public celebration of Holi?