just flew SIN-FRA-JFK early this month.
FRA-JFK segment is slightly longer than JFK-FRA but as mentioned, it is a brunch service so there will be no caviar course / no satay course.
Service wise is no different from any other segments but one disappointment is that there is no light bites available in this sector (they had to run to J class to get me a pack of chips)
There is still time for you to enjoy the bed and PJ is provided (but no amenity kit).
Not sure about SQ25 though but I understand that it is a full dinner service (hence Caviar Course) and it is a red eye flight