there's been a few "Omegas" over the years.
Opel called the platform "V"-car, first used I believe for the Opel Commodore in the earlty seventies. The history since then is something like........
Opel Commodore - two and four-door models, tie-bar front suspension & live axle rear suspension.
Opel Rekord introduced with shortened V-car platform, eventually becomes Vauxhall Carlton. Again tie-bar front suspension & live-axle rear
Senator A/Monza. Introduced in late seventies to replace Commodore. (also Vauxhall Royale) Tie-bar front suspension & independent rear suspension
Omega A / Carlton / Senator B Introduced 1987 to replace the mini V-car. independent front and rear suspension
Omega B introduced 1994. same front and rear suspension carried over.
interestingly, Opel also exported the platform to Australia, where it became the large Holden, surviving with the tie-bar front suspension until 2002, when the late V-car independent front suspension made an appearance. Also became Pontiac GTO / Chevrolet Caprice.