so many symbols in the plates.
The KE stands for Kerry. There are 26 counties in the Republic of Ireland so depending on where the car was first registered you'll have the letters for the county on the plate. The full name of the county is written in Irish above the number. The numbers represent the year and whether the car was registered in the first half or second half of that year and the final digits show where it falls in the sequence of cars registered. Unlike Poland, the plates go with the car for life
would i be okay to use someone else's vehicle if they have AC or OC insurance.
You can check their insurance documents or they can call the insurance company and check. In Poland it's the car that's insured and not the driver, so it should be ok, but check first.