When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

Can you place three balls such that the equation shown in the picture holds true?

What Adam and Eve do not have but the rest of the people have?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

I am thinking of a five-digit number such that:
The first and last digits are the same, their submission is an even number and multiplication is an odd number and is equal to the fourth number. Subtract five from it and we obtain the second number. Then divide into exact halves and we get the 3rd number.

What number I am thinking of?

That attorney is my brother, testified the accountant.

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

Who is lying?

They are three errirs in this question. Can you find them?