What does this simple rebus mean?

I have feet, but no legs. Which animal Am I?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

Which wheel of car does not rotate when you turn your car right?

The pound is not a finish.

We are sharing a few instructions below, which you have to use in any suitable order to modify the above sentence such that the end sentence is a scientific fact.

- Eliminate a letter and supplement another in its place.
- Take away one word.
- Remove one letter from one word.
- Get rid of two letters from one word.
- Swap a word with its antonym.

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

The doctor prescribed you to take one pill from the bottle every half an hour. The bottle is now left with only three pills.

How long do you think you have before you run out of pills?

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

Can you find the largest Three-digit number whose sum is 14 and whose square is less than 5,00,000?

I cannot talk, but I always reply when spoken to. What am I?