What goes up but never comes down?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

I purchased an awesome ice cream cone having 5 different flavour scoops.
Five flavours are pistachio, mint-chip, strawberry, marshmallow, and raspberry

I will give u some clues so that you can figure out the order of flavours from bottom to top.
1. The bottom flavour of the cone has 10 letters.
2. The marshmallow scoop is between the pistachio and the mint-chip scoop.
3. marshmallow is the raspberry scoop but below the mint-chip scoop.

So can you figure out the flavour of ice cream in order from bottom to top?

An evil man kidnapped someone and made them take one of two pills. One was harmless, but the other was poisonous. Whichever pill the victim took, the kidnapper took the other one. The victim took their pill with water and died. The kidnapper survived. How did the kidnapper get the harmless pill?

Replace the question mark with the correct number in below Picture:

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

What can you deduce from the following BrainBat?

CRY
LMKI

Why do people go to bed?