What does this simple rebus mean?

When it's bad luck to meet a black cat?

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?

Do you know who was buried in John's tomb?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

Which city is three-fifths chick two third cat and 50% goat?

I have teeth but i don't bite. Who Am I ?

Consider this about a word: The first two letters signify a male, the first three letters signify a female, the first four letters signify a great, while the entire world signifies a great woman. What is the word?

Can you find out a way through which you can make five squares out of the given figure by moving just six match sticks?