The option "1 and 2 only" is correct because both Donyi Polo Airport in Arunachal Pradesh and Kushinagar International Airport in Uttar Pradesh were developed as Greenfield projects, meaning they were constructed from scratch on previously undeveloped land. In the context of UPSC Prelims, this signifies India's push towards improving infrastructure in underserved regions, enhancing connectivity, and promoting economic development, as highlighted in various policy initiatives aimed at fostering regional balance and accessibility in transport facilities. In contrast, Vijayawada International Airport was not a Greenfield project, as it was developed through the expansion of an existing facility rather than on new land.