What is the word or phrase?

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

O T T F F S S ?

In a guessing game, five friends had to guess the exact numbers of apples in a covered basket.
Friends guessed 22, 24, 29, 33, and 38, but none of the guesses was correct. The guesses were off by 1, 8, 6, 3, and 8 (in random order).

Can you determine the number of apples in a basket from this information?

If an electric train is travelling south, then which way is the smoke going?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

What is the fastest way to double your money?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

Can you count the number of squares in the given picture?

Nodes are shown below and you need to connect them based on the following rule: Every node can be connected to the number of nodes inside them, i.e. the first node there is a value of 1 which indicates that the first node can connect to exactly one node only.Can you do it?

I have eight fingers and two thumbs but I do not live. What Am I?