Most players do not really know the best combo for the cars in the different terrains. So, for the grass terrain, the best combo is level 2 for engine, level 10 for suspension and level 1 for tyres. For snow terrain, level 10 for engine and suspension and level 1 for tyres. For mud terrain, all level 10. Basically, play the grass terrain using the above combo and get a score of 150 metres to unlock the mud terrain. From there, using the above combo, play the mud terrain to get all achievements in hill drive. I had used this method and got my achievements in hill drive.