Moto G5 3GB RAM dimensions are 144.3 x 73 x 9.5 mm.
Yes, you can update this phone. However, this phone comes with latest Android 7.0 Nougat out of the box. So, you may not require to update the phone immediately.
Moto G5 3GB RAM variant has 16GB internal memory.
Motorola G5 3GB RAM variant is available in 2 different colors - Lunar Grey and Fine Gold.