Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

If,

20 % 5 = 24

21 % 7 = 33

42 % 6 = 67

Then;

66 % 6 = ?

This is a simple one. You just have to count the number of Fs in the given sentence.

Finished Files are the result of years of scientific study combined with the experience of years.

How many did you count?

Move four matchsticks to the below square to form three squares?

You board a train. The train will have to enter a tunnel soon. You are claustrophobic. Which place is the best for you to sit?

What runs around the whole yard without moving?

Only one color, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

What occurs twice in a week, once in a year but never in a day?