What has many keys but can’t open a single lock?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

What do you answer even though it never asks you questions?

What word begins and ends with an E, but has only one letter?

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

The ages of a father and son add up to 66.
The father's age is the son's age reversed.
How old could they be?
(3 possible solutions).

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?