How can you take 2 from 5 and leave 4?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

Can you figure out the logic I used to decide the order of the following words:
gun, shoe, spree, door, hive, kicks, heaven, gate, line, den

Three cars are driving on a track that forms a perfect circle and is wide enough that multiple cars can pass anytime. The car that is leading in the race right now is driving at 55 MPH and the car that is trailing at the last is going at 45 MPH. The car that is in the middle is somewhere between these two speeds.
Right now, you can assume that there is a distance of x miles between the leading car and the middle car and x miles between the middle car and the last car and also, x is not equal to 0 or 1.
The cars maintain their speed till the leading car catches up with the last car and then every car stops. In this scenario, do you think of any point when the distance between any two pairs will again be x miles i.e. the pairs will be x distance apart at the same time ?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

What do you answer even though it never asks you questions?

What always comes into a house through the keyhole?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?