What made possible to read longer inscriptions of ancient India in the northwest, written in Kharoshti script?

When Prinsep identified the language of the Kharosthi inscriptions as Prakrit.

The correct answer is Option 2 - When Prinsep identified the language of the Kharosthi inscriptions as Prakrit.

The story of the decipherment of Kharosthi, the script used in inscriptions in the northwest, is different. Here, finds of coins of Indo-Greek kings who ruled over the area (c. second-first centuries BCE) have facilitated matters. These coins contain the names of kings written in Greek and Kharosthi scripts. European scholars who could read the former compared the letters. For instance, the symbol for “a” could be found in both scripts for writing names such as Apollodotus. With Prinsep identifying the language of the Kharosthi inscriptions as Prakrit, it became possible to read longer inscriptions as well.