I am quite hot but become too cold if you remove the first two letters. What am I?

Which number should replace the question mark?

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

A man wants to cross the pit of fire which is 25 feet in length and he has 2 planks(fire resistant) 19 feet in length. How can he cross the pit of fire alive?

What is both possible and impossible at the same time?

A man in a car saw a Golden Door, Silver Door and a Bronze Door. What door did he open first?

A man is shown a portrait painting. He looks closely, then tells, “Brothers and sisters have I none, but that man’s father is my father’s son!” Who is the man in the portrait?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

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 ?