Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

No matter how little or how much you use me, you change me every month. What am I?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

Three ants are going up a hill, one behind the other. The last ant then says to the other ants, 'There is an ant behind me!'' How come?

If Rajina's daughter is my daughter's mom, who am I to Rajina?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

Can you find the mistake in the below statement?

If we change the South-East direction into North and North-East into West and all others similarly.
Can you find out which direction will be in the place of South-West direction?

I can be cracked, made, told, and played. What am I?

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?