I have used Methyl Chloride strippers to remove products such as danish oil from worktops in the past. I have never used it to specifically remove OSMO though.
It was the active ingredient in the old skool paint strippers but became a restricted item because of concerns about it being carcinogenic.
IIRC correctly it is a trade only item and the minimum unit size is 5L. At one point you could purchase smaller quantities via sites such as ebay- but I think that they may have clamped down on that over the last few years. It is still used regularly by metal working shops as a degreaser.
If you want to sand it back, I would recommend 80 grit on a random orbit sander, preferably connected to a vacuum (to suck the sanded finish away and reduce the sandpaper clogging).
If you are sanding by hand, stick with 60-80 grit paper. Then finish with 120 grit. Unfortunately not all sandpapers are created equal, some will clog faster than others. Equally some (read: many become blunt faster than others). My local decorators' merchant (Leyland SDM) sell the yellow Mirka Hiomant- it is awful. The same manufacturer does however make some excellent abrasives, such as
An all-round product for various wood sanding applications. The open coating makes Avomax Antistatic especially efficient for sanding materials that clog easily. Works well for sanding soft materials and resinous wood types such as pine wood. The strong antistatic paper provides dimensionally...
www.mirka.com
The grit stays sharper for longer and it is less prone to clogging.
Edit- the paper does however smell like cat pee
