What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

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

Find the Goldfish below the given Image.

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

Can you tell a 3D object that has just two surfaces?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

Readers with excellent focus can find three differences between the camping scene pictures in 16 seconds. Can you? Test your eye power now!

In the addition below, all digits have been replaced by letters. Equal letters represent equal digits and different letters represent different digits.
ABCABA
BBDCAA
ABEABB
ABDBAA
------- +
AAFGBDH
What does the complete addition look like in digits?

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?