Simple Q&A for Pathfinder 3: Find With a Vengeance

[Yanisa]

A151
Yes, if a creature has an action that deals damage and the grab special ability, you can avoid both the grab and the damage. (Similar to poisons, trips and other side effects.) Do keep in might the damage is a prerequisite (So no avoiding grapples.)

A152
Judging from the way a Haver Sack works, it is a use activated item. Thus we get this little rule:

Use activation doesn't mean that if you use an item, you automatically know what it can do. You must know (or at least guess) what the item can do and then use the item in order to activate it, unless the benefit of the item comes automatically, such as from drinking a potion or swinging a sword.

As far as I can most benefits from the Haversack are automatic (the storing of items and the reduced weight always happen). The retrieving part is slightly more complex, looking back at the Haver Sack.

While such storage is useful enough, the pack has an even greater power. When the wearer reaches into it for a specific item, that item is always on top.

This sounds similar to "swinging a sword" idea. Just by using the normal non magical item version as intended (retrieving items from a backpack), you get the magical benefit (the item lays on top), but you need to know what you are reaching for. This do leads to some silly side effects, as in the bag looks empty to the uneducated eye and any item he puts into it seemingly disappears.

The short answer: if the user knows what items are in the bag, he can retrieve them, without even knowing it is a magic item.

A153
The skill ranks of the new class. (The idea is pretty similar to Hit Points.)