I have an eye but still cannot see.

Who am I?

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

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

What goes up but never comes down?

A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?

A dying old man wants to divide his entire land between his only two sons. Since his only wish is to treat them as equal as both of them have been too good to him, he wants to divide his land equally between them. The problem is that the land is significantly irregular in shape and thus there is no choice of cutting them into two equal halves.

Can you help him divide the land in a manner that both of his sons will be happy?

Find the missing letter in the last circle logically in the given below picture.

If all Goats are Sheep and all Sheep are Deers, are all Deers Goats ?

Solve the following series:
AZ, GT, MN, __, YB

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title