In case of missing budget (as in case of early F.3 era) or airshows etc, the FSO is replaced with a realistic looking mock-up. In case of the C101 and the SP3 pylon test, the FSO was removed entirely. The very early Rafale standard (M LF.1) also lacked FSO entirely, but was refitted to F.1 later.
Yes the Mica IR can be fired via the IRST, however the IRST must have locked the target and the lock must be direct for the Mica. The IRST does not give a datalink because it does not allow to give a distance, only a direction
Concerning the capabilities of the OFS they are very similar to those of the Pirate of the Eurofighter
The LRF would have about 40km of range at most while the IRST has about 100, for short distance shots it could work (due to the lack of sources I will not comment on it because I honestly know nothing about it) and for long distance shots it would just be impossible
No worries. In any case it is very complicated to find real official sources for the Rafale, the plane is very protected in terms of information concerning it.