In my limited experience trying to service Sunrace freewheels I was unable to remove both the cogs or the bearing retaining ring. The challenge with cog removal was caused by the profile of the "HG" type teeth. They won't fit in my freewheel vise very tightly, thus they slip, and the top cog cannot be loosened. IIRC, the bearing retaining ring would not budge no matter how long or hard I hit it with a hammer and punch.

If you want to send me your Sunrace freewheel to see if I have better luck with it, I'd be willing to take it on and let's see what I can accomplish. The worst you are out is the cost of shipping. I'll even cover return shipping if I'm unsuccessful.