Some questions about them.

1. Are they the highest power in TES? As in above Akatosh, Talos and all the others?

2. Have they always been or were they created?

3. How much damage could you actually do with an elder scroll?

4. Why can't I use it as a shield?

1. It's believed that they are the most powerful objects in Tamriel because they can reveal all possible futures in every dimension.
2. as far as we know they've always been
3 and 4. I don't think you could break one and using one of the most valuable things in Tamriel as a shield would be an idiotic move.

For 3, I mean that if say a powerful necromancer got a scroll, what could he do with it?

Blind himself ineffectually.

Any one more competent would probably use the scroll for something a bit more then raising a corpse. I figure some would probably try for actually bringing back the long since dead since we've seen the attempt end in spectacular failures, but I wager it wouldn't end to well either. In truth, the blasted things are probably very hard to use willy nilly.