What always comes into a house through the keyhole?

What has no start, end, or centre?

What is the next number in the series?

15 29 56 108 208 ?

Living above a star, I do not burn
Eleven friends and they do not turn
I can just be visited in a sequence, not once or repeatedly
PQRS are my initials
Can you tell my name accurately?

Can you find the six hidden animals in the picture below?

Replace the question mark with the correct number below.

If,

A = 1

B = 2

C = 3

...

...

Z = 26.

Based on above rule, you need to find an eleven letter word whose letter sum is equal to 52.

Through your logical capabilities, can you make 7 an even?

I am white when I am dirty, and black when I am clean. What am I?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?