Birbal – The neighbour should take the water with him since the well belongs to farmer.

Brian,
Only Brian speaks truth.

Adam is lying about Brian.
and Also Cody Is lying since Brian does not lie. Thus Brian is the one speaking truth.Any other combination will fail to come out true.

The man said, ‘I will be killed by giving poison.’

If Akbar says the statement is true, the man will be killed by hanging which will make his statement false.
If Akbar says the statement is false, the man will be killed by giving poison which will make the statement true.

Thus Akbar had no choice but to leave the man unpunished.

Four

As the window was closed it is obvious that the six candles that were not extinguished were lit till they melted away entirely. Thus only four candles that were extinguished remain at the end.

This time is not permanent, It will change very soon

Nothing is permanent neither good nor bad time.

“This time will pass soon.”
“यह वक्त भी गुजर जायेगा।”

Steps to measure 15 minutes

1. Light Rope #1 from both ends.
2. At the same time light Rope #2 from one end.
3. When Rope #1 burns fully, it will be 30 minutes and Rope #2 will take 30 more minutes to burn, light the other end of Rope #2 at this time, thus it will take 15 minutes to burn.
4. Start cooking your egg at the same point.
5. Stop cooking when Rope #2 burns fully.

The fewest number of aircraft is 3!

Imagine 3 aircraft (A, B and C). A is going to fly round the world. All three aircraft start at the same time in the same direction. After 1/6 of the circumference, B passes 1/3 of its fuel to C and returns home, where it is refueled and starts immediately again to follow A and C.

C continues to fly alongside A until they are 1/4 of the distance around the world. At this point C completely fills the tank of A which is now able to fly to a point 3/4 of the way around the world. C has now only 1/3 of its full fuel capacity left, not enough to get back to the home base. But the first ‘auxiliary’ aircraft reaches it in time in order to refuel it, and both ‘auxiliary’ aircraft are the able to return safely to the home base.

Now in the same manner as before both B and C fully refuelled fly towards A. Again B refuels C and returns home to be refuelled. C reaches A at the point where it has flown 3/4 around the world. All 3 aircraft can safely return to the home base, if the refuelling process is applied analogously as for the first phase of the flight.