What's the only room from which no one can enter or leave

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

Doctor Alex and a bus driver John are both in love with the same woman named Olivia. The bus driver need to go for a long trip of 10 days, Before he left he gave Olivia 10 apples.

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

In a rainy season, one day 3 huge ladies walked under a normal-sized umbrella.
The umbrella is not huge enough to accommodate all 3 ladies yet not a single lady got wet. Why?

Pronounced as 1 letter, And written with 3, 2 letters there are, and 2 only in me. I’m double, I’m single, I’m black blue and grey, I’m read from both ends, and the same either way. What am I?

Count the number of lines in the image below ?

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