Solution:

Youssef is name of a man , and out of 11 people only one is male

Solution:

Rhea will open just one present.
Cindy|Y - Y is the 25th alphabet
Duk|E - E is the 5th alphabet
Joh|N - N is the fifteenth alphabet
Rhe|A - A is the first alphabet

Solution:

This can be done if you draw a five pointed star and place the balls on the corners and intersection points. See the figure to understand better.

Solution:

A cigar stuck in the wall

Solution:

I filled a glass full of water and held it over my head for 20 minutes.

Solution:

-3 -1 1

Explanation:
-3 * 1 * -1 = 3(prime)
-1 - (-3) = 1 -(-1) = 2

Solution:

199 - 99

Solution:

He askes the god to beat him half to death.

Solution:

XIX is the answer which refers to nineteen in roman numeric system. On taking out one i.e. I, we will get XX that is equal to twenty.

Solution:

Pages 19, 20, 23, 37, 38, & 42 will also be missing

Solution:

The two numbers are 4 and 13 whose product is 52 and sum is 17.