IFR and IF
As I understand it IFR refers to the RULES (and airspace etc) under which you fly. IF refers to the conditions. If you have one of those large (sort of A4 ish) JAA logbooks you will see two columns for both, and yes a separate column for night.
Frankly I have stopped logging IF time since the vast majority is with the autopilot on; if I'm IMC at FL250 and 'George' is flying can I really take the credit especially when it's multi-crew. So my IF column has not seen ink for a while but my IFR column is nearly always filled in, in parenthesis to the actual flight times for the trip.