1) When the shark feed on the boy would there be much left after it has finished feeding, for the rescuers to find?
No, there wouldn't. A smaller shark would proabbly leave the ehad, but this one is big enough and with big enough jaws to eat everything.
2) When it starts to feed on the boy’s brief red shorts, what all will it eat in that mouthful?
Due to the shark's size, probably everything in one bite - shorts, private parts, buttocks.
3) If the shark was large enough, could it swallow all of the small red shorts and what was in them in a few gulps?
Yes, it would take them in its mouth, chomp a couple times, then gulp a few times.
4) I would imagine the shark will not need to eat for some time after it eats the boy?
They usually feed twice a week, so it will probably need another meal in 3-4 days.
5) How long would the rescuers /searchers have to find and catch the shark before any trace of the boy would be gone?
By the time the meal went through the stomach and intestines 3 nor 4 days. However, what woudl be left of him at the end of that time period would just be mush. DNA testing would identify human remains.
6) Is there any way they could catch the shark alive and pump out it`s stomach to see if it had eaten the boy, if so what all will they find if it was caught 24 to36 hours after the attack?
Bones and mushy stuff that might be identfiable as human remains. If not, DNA testing woudl prove it.