No
Yes sort of.
Yes, No
Flashing is fairly safe if you are careful to leave discs out and ALWAYS identify the correct drive. I flashed my old 812 back and forth more times than I can remember and it took every time.
Also there are many DOS recovery utilities in case of emergency as the Liteon is the best supported drive in this forum
If you screw up, you void your warranty but most people here would say that you are being ethical if you try to flash different firmware to fix a problem and then go back to stock before you RMA.
Windows flashing works, go here for almost all the files you will need.
http://codeguys.rpc1.org/firmwares.html