Re Police:
When only BA did Belfast they had to depart and arrive from the Causeway Lounge (Gates 1-3 T3).
When WW started BFS they could depart from a selection of T1 gates but had to arrive at G3 T3.
BA complained (!) about an un-level playing field (!) so the Police check was moved to the T3 security area, allowing BA to depart Belfast from any gate. But arrivals were still to be via T3 G3.
I understand the Police are moving to somewhere around G43 on the arrivals level so a/c can arrive at any gate and the passengers be bussed in with a shorter walk.
The Police check in T1 is now in the arrivals hall, to which passengers will be bussed. This replaces the ludicrous arrangement next to Immigration, where passengers just used their passports and bypassed the check, by going through Immigration with international passengers.
There is no Police check in T2 any more because there are no flights of interest to the Police since FR moved to T1.
Having said that the Police can do what they like if they really want to!