Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?

Christina is older than Kareena and Karishma. Katrina is older than Karishma and younger than Kareena. If Kareena has a brother named John, who is older than Christina, who's the youngest?

Can you move 2 matchsticks to form four equal sized squares.

What has one letter and starts with an E?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

Take away the whole and some still remain. What is it?

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

Suppose that you are trapped on the surface of a frozen lake. The surface is so smooth and ideal that there is no friction at all. You cant make any grip on the ice and no wind is blowing to help you out. You have just a mobile phone with you which has got no reception disabling you to call for help.

How will you plan your escape before you freeze to death on the frozen lake?