You should be able to check it only to FRA, just tell the agent to " short-check" until
there. Highly doubtful that you will get all the boarding passes, probably only for
the first 2-3 flights.

Last week I flew YYZ-(AC)-SFO-(UA)-HKG-(SQ)-SIN-(SQ)-CGK.
At YYZ, they were only able to check the bag as far as SIN, and only issued the first
2 boarding passes. When I stopped at the transit desk in HKG for the next boarding passes, I asked them to retag the bag to CGK, which they did, and I was given a new
luggage tag at the gate in HKG.