Engine oil drain is under the center of the engine. Look for the access hole in the skid plate. Same with the differentials.
The engine holds just over 2 quarts. The differentials each hold a little less than half a quart. If I remember correctly the fill hole in the rear differential is tiny and at an awkward angle.
if you look in your operators manual it tells you where the plugs are and the amount of oil each takes,you fill the engine through the dipstick tube and oil filter is on the back of the engine accessed from passenger side,the filler plug on the the rear diff is smaller than the front diff,only takes one liter between front and rear diffs,i buy the yamalube kit and diff oil from my dealer and has some of the plug washers with it.
Only 6 locations. 4 on rear knuckles and 2 on front drive shaft. On front drive shaft - 1 in front next to diff easy to get to from front driver side and 1 just in front of the airbox.. harder to get to. I use a Marine grade grease to keep it from just washing out.