Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

A cricket has 6 legs, a squirrel has 4 legs and a spider has 8 legs.

In a local zoo, it was found that the total number of legs is 612. Also, there are equal number of each of the above animals/insects.

Can you find out how many animals are there in the zoo?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Can you find the 09 errors in the picture below?

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?

You have 1023 apples and 10 bags. You have to distribute these apples in these 10 bags in any way you choose. But when I ask for a certain number of apples you have to give them in terms of bags without transferring the apples from other bags. How do you distribute the apples?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

My cousin lives in one story house in Antarctica. His house is made the of-of sandstone. what is the color of stairs?