[RPG] Does resist all prevent normal damage

Nope

Unless it specifically says otherwise they do not stack. It's item 28 on the PHB FAQ over at Wizards.com.

Note that this applies to all resistances, so you'd only get the Resist 10 All.

Edit:

Here's a snippet from the Compendium entry that is linked in the FAQ.

Not Cumulative: Resistances against the same damage type are not cumulative. Only the highest resistance applies. For example, if you have resist 5 cold and then gain resist 10 cold, you have resist 10 cold, not resist 15 cold. Similarly, if you have resist 5 cold and then gain resist 2 to all damage, you still have resist 5 cold, not resist 7 cold.

It’s not really a property of being untyped that ignores DR (that's more relevant for ignoring resistance/immunity), it’s just the fact that physical attacks are always bludgeoning, piercing, and/or slashing, and thus the only things that deal with DR are also never going to do untyped damage, and the things that do use untyped damage are the things DR doesn’t apply to.

But Paizo isn’t interested in being clear or precise, and likes to treat off-the-cuff developer comments as official rules of the game, so, this kind of confusion is just a part of the game.