These types of puzzles are known as charades. What you have to do is to find two words that are referred to in the first stanza and the second stanza and put them together to form the third word in the third stanza.

Just for example, if my first refers to ‘off’ and my second refers to ‘ice’, then my whole will be the ‘office’.

My first is present – future’s past –
A time in which your lot is cast.

My second is my first of space
Defining people’s present place.

My whole describes a lack of site –
A place without length, breadth, or height.

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?

I look at you, you look at me I raise my right, you raise your left. What am I?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?