Hi,
a) As stated by Mar, FMN4N is to be executed for reconstruction of POs.
b) FMAF, normally, is not necessary after running FMN4N
c) FMAVCREINIT cannot harm your system and you'd better to execute it. It is advisable to schedule it, when no activities are being performed. Though, even if they are, the maximum 'danger' is that these transactions would be blocked.
d) If you have flexible budgetary system; where budget addresses are changing frequently, it is even advisable to run FMAVCREINIT on regular basis. For more info, check note 725266.
Regards,
Eli