What is both possible and impossible at the same time?

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

When a clock is observed, the hour hand is at a minute mark and the minutes hand is six minutes ahead of it.

When the clock is observed again after some time, the hour hand is precisely on a different minute mark and the minute hand is seven minutes ahead of it.

Can you calculate how much time has elapsed between the two observations?

What am I?

John can fit six large chocolate boxes or nine small chocolate boxes into a carton. How many cartons will he require to put sixty-six chocolate boxes into?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

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?

What does the below rebus puzzle mean?