Yes the Browning Diana grade choke tubes are compatible with Invector Plus shotguns
From what I am seeing on Browning's website, the Browning Cynergy uses Invector-Plus choke tubes.
Porting might reduce recoil and muzzle jump a tiny bit, but many people feel it's not worth the increase in noise from blasting shot gases out to the side. It's not that big a deal if you're shooting clay targets where everyone is wearing hearing protection, but if you're hunting--especially over a dog--with others, ported guns are often not welcome.
These Browning Diana Grade Extended Choke Tubes will not work with a G Force 12 gauge. That shotgun uses Beretta/Benelli MobilChokes which can be found at the link below.
https://www.opticsplanet.com/carlsons-12-gauge-benelli-beretta-sporting-clay-choke-tubes.html
Yes, the 28 gauge models should fit.
Yes, you can.
The exit diameter for the 12 gauge would be approximately .705 and these Diana Extended Invector-Plus chokes do not come in an extra full.
These choke tubes are Invector-Plus and the Citori 725 uses Invector-DS chokes. Standard Invector, Invector-Plus and Invector-DS chokes do not interchange.
Browning does not recommend using steel shot in these chokes.