1. Mileage will improve is engine is run in. Give it time.

2. The MRV is a car-based 4X4 and and doesn't have low-range gearing as a proper off-road vehicle should. I wouldn't advise dune-bashing per se but you can take it off road.

3. Like all 4X4s it has a higher center of gravity so take it easy around corners! It weighs more than a car so take that into account while braking as braking distances are longer.

Enjoy.