に vs で (location particles)

"I wonder what's going on inside the cave? I really want to know." "I have no idea."

A million people lost their lives in that war.

Mother always wears a kimono at home.

That's where the problem lies.

Where do you live?

We had a meal at our uncle's place.

You must not ride bicycles on the sidewalk.

She wrapped the gift in paper.

I was in the mountains.

When I woke up, I was lying on the floor.