Yes, permission is necessary to fly drones in Nepal. In fact, one should register their drones with the Civil Aviation Authority (CAAN).
The cheapest DJI drone is DJI Mavic Mini Standard which costs around RS. 41500.
A quadcopter is an uncrewed aerial vehicle or drone with four rotors, each with a motor and propellers. Whereas Octo copter is a type of drone having eight blades. A quadcopter is more efficient than an octocopter.
DJI Drones are one of the best brands in Nepal as of now. DJI Drones come with varieties of models and one can find the perfect model at a great price in Nepal.