I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?

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

Find the number of squares in the below picture

I am white when I am dirty, and black when I am clean. What am I?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

A man walked into a pub and went straight towards the Barman. He asked for a dirty martini from the Barman. The Barman thought something and then pulled out a pistol from his drawer and aimed it directly at the man. Why did he do that?

What has a ring but no finger?

Why do we preferably have round manhole covers and not square ones?

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _