can I wear a unit citation awarded during combat operations?

No, the uic's are different. I was on a rear detachment when my unit deployed. If they were to get a unit citation the orders were usually say the unit forward.

Below is from the HRC Awards FAQ page.

Q8: For a Soldier to receive a Meritorious Unit Commendation (MUC) as a permanent award, did the Soldier have to have served in theater with the unit or could he have served in the rear detachment?

A8: The Soldier must be deployed to the area of operations where the MUC was awarded. Please refer to Table 29-1, AR 670-1 for criteria on wear of unit awards.

https://www.hrc.army.mil/content/Unit%20Award%20Info

The proof of unit award is usually the deployment order that put you with that unit in that country in the time frame of the unit award.

From HRC:
"A unit award is awarded to a designated unit and is worn by members of that unit who participated in the cited action. Personnel who did not participate in the cited action, but who are assigned to the cited unit, are authorized temporary wear of the unit award while assigned."

Read the regs. If the unit is awarded say the MUC, then everyone assigned to that unit forever will wear the MUC. Now if you were in the Unit when it earned the MUC, it is like a personal award and you can wear it till you die.