Option 4 -> By re-purposing the fourth stage of the launch vehicle as an orbital laboratory -> correct
The passage explicitly states: "The ingenuity of this mission is further demonstrated by ISRO's decision to re-purpose the fourth stage of the launch vehicle as an orbital laboratory." This innovative approach of transforming what would typically be space debris into a functional orbital laboratory showcases ISRO's forward-thinking mindset and commitment to sustainability, turning challenges into opportunities while advancing scientific capabilities.