What does below chemistry rebus means?

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?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

What occurs twice in a week, once in a year but never in a day?

Can you solve this picture maths equation?

A cat had three kittens: Snophy, Topsy and Jorden. What was the mother's name?

An octopus has 8 legs. A hippogriff has 6 legs and 2 pairs of wings. A sphinx has 6 legs and one pair of wings. Now we have all 3 kinds and a total of 18 insects in a cage. We have a total of 118 legs and 20 pairs of wings. How many insects do we have of each kind?

That attorney is my brother, testified the accountant.

But the attorney testified he didn't have a brother.

Who is lying?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?