The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

The following sentence is false. The preceding sentence is true.
Are these two sentences true or false?

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?

Rob is taller than Edwin, and Jurgen is shorter than Rob.
Of only one of the following statements, we now certainly know it is correct:

A.Edwin is taller than Jurgen
B.Jurgen is taller than Edwin
C.It cannot be determined if Jurgen or Edwin is the tallest.

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

If we tell you that there is a relation between the numbers and letters in the given figure, can you analyze it and find the missing letter in the last box?

My cousin lives in one story house in Antarctica. His house is made the of-of sandstone. what is the color of stairs?

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.