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

In the given picture, you can find two letters missing. When two particular letters are placed in the missing spots, you get an eight-letter word while reading in the anti-clockwise direction. Can you find out the missing letters and the missing word eventually?

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

Which is the smallest number that you can write using all the vowels exactly once?

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

Can you replace the X (both small and big x) with the numbers between 1 to 19 such that all the rows of 3 numbers between X (big x) sum to 23?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

Speaking of rivers, a man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

Teacher ask the student

'Why are you standing on that chair in music class ?'.

what did student replied ?