Q. If I increase my Constitution score so that my modifier increases, do I gain extra hit points per level for all of my past levels?
A. Yes. The only special case in which a raised modifier does not affect previous levels is your Intelligence's effect on Skill Points.

Q. Does an invisible opponent get to Sneak Attack his victim, even if his chosen victim has already acted in the round, and thus is not caught flat-footed?.
A. Yes. If the attacker is invisible, the defender loses any Dexterity bonus to Armor Class (against the invisible attacker only), which is one way of gaining the Sneak Attack option (provided the attacker has this ability in the first place).

Q. Can I use the Spellcraft skill to identify a spell an enemy is casting even though it is not yet my turn to act in a combat round?
A. Yes. No action is required, although you must be able to see or hear the spell's somatic or verbal components, respectively.

Q. I don't understand the rules regarding missing with ranged attacks and where the missile might hit.
A. Don't worry. I'll be designing a simpler system soon.

Q. Do I have to continually concentrate to maintain the spell Spiritual Weapon?
A. No. The only concentration required is when you wish to redirect the weapon to a new target.

Q. Can I direct a creature that I summon with the spells Summon Monster I through IX?
A. Yes, but only if you can communicate with that type of creature. Otherwise the summoned creature attacks your opponents to the best of its ability, making decisions on its own.