The Pragyan rover installed in the Chandrayaan-2 mission had 6 wheels. The rover was designed to traverse the lunar surface and carry out scientific experiments. Having 6 wheels allows for better stability and mobility on the uneven and rocky lunar terrain.

Option 1: 2 wheels - This is incorrect. If the rover had only 2 wheels, it would be less stable and have limited mobility.

Option 2: 3 wheels - This is incorrect. Having an odd number of wheels would make it challenging for the rover to maintain stability and balance.

Option 3: 4 wheels - This is incorrect. Though having 4 wheels is more common for rovers, the Pragyan rover specifically had 6 wheels.

Option 4: 6 wheels - This is the correct answer. The Pragyan rover had 6 wheels, which allowed for better stability and mobility on the lunar surface.

In conclusion, the Pragyan rover installed in the Chandrayaan-2 mission had 6 wheels.