Answer:
One simple click, one simple flash. A piece of memory, for years I'll last. What am I?
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. Sooner or later everybody needs my help yet many people are afraid to let me help them.
To cross the water, I'm the way. For water I'm above, I touch it not and truth to say, I neither swim nor move. What am I?
I need to be taken before you can have me. What am I?
I may seem real but it always turns out I was never there in the first place... you only see me during a certain resting stage.
Give it food and it will live, give it water and it will die.