There are many factors to be considered. That would be too much weight for most people to be considered safe or healthy. Unless you are several hundred pounds overweight, it would not be feasible. About half that could be done, but it is still a lot. A weight loss of 1 to 2 pounds a week is normally considered safe.
Yes.
Exercise. Lots of it.
Hardcore exercise
it really can be possible if you try hard and believe that you can do it.
It is not safe to lose 90 pounds in only 4 months unless under a doctor's direct care.
4 weeks in a month. 12 weeks. 24 lbs
64 ounces = 4 pounds
You are not fat if you are 12 and weigh 118 pounds at 4'12. The maximum for that height is 127 pounds. To lose 20 pounds in 4 months, restrict calorie intake and increase cardio activity.
Four pounds.
~3200 of pure fat.
if you lost 4 pounds each week and you wanted to lose 40 than you would have to do that for 10 weeks.
You cannot lose 50 pounds in 4 weeks by any natural means.