Which number should replace the question mark?

What does the below rebus riddle means?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

This is a picture puzzle. You have to guess the name of the movie that can be related to the picture.

What is the centre of gravity?

The following "Brain Bat" means Slow Down.
S
L
O
W

Using the same logic, can you tell us what does the following Brain Bat means ?
E
V
I
G

Which digit occurred maximum times between the number 1 and 1000?

I welcome the day with a show of light, I stealthily came here in the night. I bathe the earthy stuff at dawn, But by noon, alas! I'm gone.

There is an exact a week gap between Christmas and New Year. Hence, It is obvious that the new year that comes right after Christmas comes on the same day of the week.

A Strange thing happened in the Year 1777. Christmas occurs on Wednesday and New Year on Monday. How is that possible?

A man looks at a painting in a museum and says, “Brothers and sisters I have none, but that man’s father is my father’s son.” Who is in the painting?