How does one remove the lockring and sprockets from a Shimano MF-HG20 freewheel? Getting the freewheel off the hub is no problem; what I want to do is to get the sprockets off the freewheel.

I have tried tapping the lockring in an anti-clockwise direction with a steel punch, but it refuses to move. The markings on the smallest sprocket suggest that all the sprockets are splined.
The lock ring should thread off anti clockwise. You’ll have to hold one of the sprockets with a chain whip to keep the whole body from turning. If you have a lock ring tool, that makes it easier.