I shave every day, but my beard stays the same. What am I?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

I am the largest in my family of fifty.
The youngest of our family lives separately from the rest of the family and so do I.
I am regarded as harsh and tough.
I am so large, you cut me in two equal halves,
each half would still be larger than the second largest member of the family.
Who am I?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

What is full of holes but still holds water?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?