That is what you think what China's principle is, I am afraid.
Examples include but not limited to: China recognized Bangladesh's independence from Pakistan
Bad example. China only recognized Bangladesh independence in 1976 after Pakistan formally recognized Bangladesh independence in 1971 and most of the world already recognized Bangladesh independence. So no, it's not comparable.
, recently China recognized South Sudan's breakaway from Sudan
Bad example. Sudan and South Sudan mutually agreed and permitted South Sudan to hold an independence referendum vote, which it overwhelming won. It would be like recognizing Singapore independence after Singapore/Malaysia mutually agree upon separation. It's not remotely comparable to Xinjiang or Donbass.
China's decision is NOT based on some paper or referendum but on the fact on the ground as proof of separation being acceptable.
A bloody conflict can be a proof, such as Sudan. An absolute ethnic majority can be another one such as Crimea and Donbas. Failure of the government in keeping the country together can be also one, such as breakup of Yugoslavia.
But China can refuse and has refused to recognize breakaways such as Kosovo because Serbia is our friend even though Kosovo does fulfil some said conditions (war and ethnic).
One can only be "double standard" if one breaks ones stated principle. But China has never made such statement as you suggested.
None of the examples you put forward is applicable since they are not comparable to Donbass or Xinjiang.
China doesn't need to openly support Russia in liberating Ukraine from the US puppet regime. A Russian victory in Eastern Europe will be beneficial to China. Should I remind you about how the EU and America regularly Spit on China's face in the name of Democracy? Double standards is a norm in world politics since ancient times.
That is realpolitik. China doesn't play realpolitik, as evidence by China foreign ministry's avoidance to openly support Russian actions and calling for all sides to deescalate and respect the Minsk agreement.
You are clearly just using your supposed "opposition" to double standards as an excuse to push your Pro-American narratives. You claim to support China but at the same time also support China's enemies lol.
You need to improve your logic and argumentative skills if you think just calling others a "shill" will make your points valid.
If I am a pro-US shill, then you are an pro-Russia shill. See how easy it is to use emotion and no logic? Gotta put more effort into your pro-Russia defense.