I’m tall when I’m young, and I’m short when I’m old. What am I?

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

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

What word begins and ends with an E, but has only one letter?

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

A person was found dead on a big green land with no trees or buildings around. When the police arrived, they found a piece of rock lying next to him and the man was wearing clothes comprising of red, blue and yellow colours.

Can you tell who the person is and what was the cause of death?

I know a nine-letter word having only one vowel.
Do you ?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?