When can we add 2 to 11 and get 1 as the correct answer?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

If one and a half boys, eat one and a half burgers in one and a half hours.

How many burgers can 9 boys eat in 3 hours?

What is both possible and impossible at the same time?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

A blonde put eyeliner on her head. Why?

What does this rebus mean?

O
N
C
E
TIME

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

Find out the number of circles in the given picture having Illusion

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?