Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

A person was killed at a house party. When the police arrive, there are six people present in the house who are the friends of the victim. The name of the friends is Rohit, Aman, Nick, Gagan, and Randy.

Near the dead body, they find a few numbers written with blood by the victim on the floor. The numbers are 8, 5, 4, and 11.

The police arrests one of the friends for the murder. Whom did they arrest and why?

A man dies of old age on his 25 birthday. How is this possible?

You’re out on the water and see a boat filled with people. You look away for a second and look back again, but this time you don’t see a single person on the boat. Why? Hint: The boat did not sink.

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

Aaron, Brad, Christopher, Danny and Elvis decided to play a game of tiddlywinks. In this game they decided that one win will get 1 point for winning, 0 for losing and 1/2 in case of a tie.

They finished the game in alphabetical order and it was found that the scores were different for each person.

Based on the following two statements, can you find out the result of the individual games?
Brad: No one could finish like me, without a loss.
Elvis: No one played worse than me, I finished without a single win.

What is the difference between a jeweller and a jailer?

How many triangles are there on the puzzle below?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?