What is always in front of you but can’t be seen?

What are the 50th, 63rd and 100th numbers in the sequence below?
4, 5, 8, 8, 9, 9, 12, 13, 13, 13, 17, 18, ...

Replace the question mark in the picture below.

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

Can you divide the below-given shape into four equal and identical pieces?

There are 2 cops parked along a one-way street looking for traffic violations. They spot a taxi driver going in the wrong direction, yet they do nothing.

Why?

How many triangles are there in the picture below?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Can you count the number of lines in the below picture?

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