Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

Two fathers and two sons decided to go to a shop and buy some sweets upon reaching. Each of them bought 1 kg of sweet. All of them returned home after some time and found out that they had 3kg of sweets with them.

They did not eat the sweets in the way, nor threw or lose anything. Then, how can this be possible?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

What does below Rebus say?

XLR8

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?