Solution:

The blood came from a mosquito. It bit and sucked my blood last night. It then flew and sat on the ceiling. Determined to kill it I swatted it right there and the minuscule splatter came from it only.

Solution:

Can be found on the pic below.

Solution:

Michelangelo juggles the diamonds across while crossing the bridge.

Solution:

Move and then pour all juice from second glass to fifth glass.

Solution:

A
D
C
A
B

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:

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

Solution:

f the last elf is taking some time to answer the question then it shall mean that the elf's before him are all wearing distinct coloured hats. However sufficient time shall be given to the last elf to give the answer.
If he views the similar coloured hats in front of him , he shall quickly tell the answer

Solution:

The Stars

Solution:

Blue could only be wearing white or red and we know that there is already someone else wearing the white shirt so Mr. Blue could only be wearing the red shirt.

Mr. White could have only been wearing a blue or a red shirt, and red is already taken, so Mr. White is wearing a blue shirt.

Mr. Red now has to be wearing a white shirt.

Solution:

It can be solve as shown below.