There are severel models that carry the WSM calibers. You can see the full model lineup on the current Browning on line catalog. Check the link below.
I am aware of only the following calibers in the B78: 22 250; 6mm Rem, 7mm Rem Mag; 30 06 and 45 70.
Dont believe Browning chambered a rifle for the 6mm Remington cartridge. Do you mean 6.35mm (a pistol)?
Yes.
Not currently cataloged.
Impossible to answer without the serial number
It shoots .25acp
Does not exist
yes
Yes
no
Impossible to answer without the serial number
Go to http://www.browning.com/customerservice/dategun