UpperLeftRC The motor is roughly 3 inches long

UpperLeftRC There is a brushless motor option for this car from WL toys, they make brushed and brushless options for almost all models of their RCs

UpperLeftRC No idea 🤷🏻‍♂️

BG513465721 No this model only comes fully assembled with the standard plastic and metal parts, the fully metal trailing arms and steering knuckles etc. can be purchased separately, from personal experience I would avoid the all metal upgrades, it makes the vehicle heavier and more prone to breaking during an impact, also the metal adjustable steering links do not stay adjusted correctly and vibrate while driving so it ends up ruining the steering angles and makes the vehicle impossible to drive or steer after every run you play with it, keep the stock plastic parts on the buggy and you will be way more happy with it

BG513465721 Between 20 and 25 minutes depending on how much “full throttle” you are using during the run time, if you are feathering the throttle and regulating the speed it can last up to 30 minutes

BG513465721 Yes you can use whatever brand of grease you want in the differential, it shouldn’t have a negative effect on performance at all, if anything it will increase performance and longevity of the parts.

BG513465721 The tray can be adjusted under the vehicle as well to fit the battery better

BG513465721 Unbranded 7.4v 2200mah lipo