With the help clues provided in the image, can you find the 5 digit key?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

There are four 3-link chains. All you have to do is join them into a big 12-link chain. For joining two closed links, one of the links must be cut and placed onto the other link for closing.

How many minimum links will you have to cut to make the big chain?

A man was found murdered on Sunday morning. His wife immediately called the police. The police questioned the wife and staff and got these alibis: The Wife said she was sleeping. The Cook was cooking breakfast. The Gardener was picking vegetables. The Maid was getting the mail. The Butler was cleaning the closet. The police instantly arrested the murderer. Who did it and how did they know?

Can you figure out the logic I used to decide the order of the following words:
gun, shoe, spree, door, hive, kicks, heaven, gate, line, den

John was a very careless driver, so his owner Jacob gave him an offer that he will get an incentive of Rs.30 for every bottle box he delivered without breaking it and he will be charged Rs.90 for every bottle box he broke. Jacob gave John 100 bottles-box to deliver. After delivery, Jacob paid John Rs.2400. How many bottles-box did John break?

Do you know of a place where the wind blows south and then suddenly shifts direction towards the north?

Find the combined weight of the Cat, Dog and Rabbit in the given picture.

A Club organizes a Running Race, and John, Jacob, Minda, and Tony participated.

The results are as follows

John beats Jacob
Minda beats Toni
Toni beats John

Who came first in the race?

Replace the question mark with the number below given a simple math problem.