Hello, regarding the chain skip when backpedal issue. May I know which brand of cassette are you using? I have a 16 inch bike using 10 speed sensah derailleur with sunshine cassette 11-28T has same problem. Some foreign RU-vidr said this problem was caused by the low price cassette. What do you think? And I have a 20 inch bike using 9 speed shimano derailleur with shimano cassette 11-34T no such problem.
I don't completely agree on that. Chain tension, chain ring alignment, and cassette size also cause chain skipping when backpedaling. Since it's a 1x drivetrain, it's so hard not to skip, especially when the first cog is very large and chain is too short and tight. Lengthening the chain may help. I had no skipping when using the 11-32. They are both from Sunrace. After all. It's a minor problem that I don't mind. I have a new KMC chain in spare. I think when I install it and make it longer. The problem will be effectively resolved.
But of course, making sure your front chain ring is properly aligned is also important. But as you said. If everything is done right, then it may be the quality of the cassette, in the end☺️.