It all depends on where you live. Most states in the USA do not require one but some cities do like New York and San Francisco. Other countries consider air gun and rifles to be firearms and have different laws covering the ownership of an air gun or rifle.
The Crosman Phantom is still in production and sells for $90
As far as I know the Crosman Phantom is not a BB gun but a pellet rifle. If you want to see the parts list for the rifle then see the Crosman link below.
The Crosman Phantom is designed to shoot ONLY .177 pellets NOT BB's, they will ruin the rifling in the barrel.
No it is not possible (in the USA) Crosman only makes the Phantom in a 177 Caliber. However I believe the Phantom .22 is made for Canada and Yes it will kill a bird.
I think you will have to contact Crosman directly to get an answer to this. See the link below
Crosman doesn't advertise the "Foot Pounds" of their airguns but they do state the FPS "Feet Per Second". The Crosman Phantom .22 is rated at 495 FPS. If you still want to know the Foot Pounds I suggest you contact Crosman at the link below.
The muzzle is the end of the barrel.
6.2 Lbs without scope
China
Crosman pellets are fine. however if you really want quality pellets I suggest H&N pellets
the CS6M22X I believe is the .22 version of the Crosman Phantom .177 cal rifle. See the link below for the .177 version of the parts list.
See the link below for the drawing.