Answer : 2. "अलाउद्दीन खिलजी"
Explanation :

1. The title Sikandar-i-Sani (Alexander the Second) was adopted by Alauddin, whose original name was Ali Gurshap, and Delhi was proclaimed Dar-ul-Khalifa (seat of the Caliph).

2. Using the title Sikandar Sani, Khilji minted coins.

3. Although Sani is 'second' in Arabic. In appreciation of his military achievement, the coin legend (Sikandar-i-Sani) translates to 'The Second Alexander'.