Sounds like you want back on your full time schedule instead of this new one that isn’t spelled out in the CBA. Seems like any time someone doesn’t have their hand out or complain about the job they must hate the union or be management.
The only mention of receiving differentials in CBA I can recall is during FDT. Article 34 section 6 reference changes within seven days and getting night differentials for what you would have worked.
And yes you will get paid any for any differentials you actually worked. Sundays, nights, holidays, CIC. If you are on admin you should not receive any of these.