Flash lower version will not make SIMLOCK* RPL damaged.
As well wont to be helped. Try this:
1. Backup RPL of this Phone via FBUS cable
2. Write RPL BB5 Phone RPL to this phone in order to DAMAGE NPC - chk if phone gets local mode ? If it does* read out the Full PM or PM120 only.
3. If you can get PM backup* then we can downgarde this phone and make work ;-)