Do magical weapons convey effects to magical ammunition?

Question

Let's say I have a +3 Frost Longbow.

Frost Weapon

Power (Cold) · (Free Action)
All damage dealt by this weapon is cold damage. Another free action returns the damage to normal.

Power (Cold) · Daily (Free Action)
Use this power when you hit with the weapon. The target takes 2d8 cold damage and is slowed until the end of your next turn

A normal arrow fired from the weapon gets the +3 enhancement bonus to attack and damage, and using the power of the weapon, can be converted to cold damage.

Now I want to fire a +2 Dual Arrow from the bow.

Dual Arrow

Property: When you attack an enemy using this ammunition, you can roll twice and use either result.

Since enhancement bonuses don't stack, I obviously don't get +5 to attack and damage with this attack. But my question is do I still get the +3? Or does the +2 "override" the +3? And if the answer to the second question is yes, that brings up the followup questions: can I still convert the damage from the Dual Arrow attack to cold damage? Can I still use the activated power?

To boil it down:

Which enhancement bonus do you use when you fire magical ammunition from a magical weapon?

Can you use weapon powers/properties with magical ammunition?

Answer 1

The enhancement bonuses would not stack (2 same typed bonuses). In fact the magical ammunition's enhancement bonus does indeed supersede the bonus from the weapon. The critical effect from the weapon will stack with the arrow's effect.

You can fire the magic ammo without "activating it" and use the weapon's enhancement bonuses but you cannot use the properties from the magic ammo.

The relevant section of the linked page answers the question fully and completely:

Ammunition applies an enhancement bonus to an attack roll and damage roll when used. If the projectile weapon is magical, use the ammunition's enhancement bonus in place of the weapon's enhancement bonus. The weapon's critical bonus and the properties from both the weapon and the ammunition still apply. Using magical ammunition doesn't prevent you from activating a magic weapon's powers.