It looks like China has a working alternative since 2015 [1], not sure regarding your other questions if it's in their interests to expand it or not.
[1] https://www.scmp.com/economy/china-economy/article/3168684/w...
[1] https://www.scmp.com/economy/china-economy/article/3168684/w...
Would you trust the yen? Or the ruble?
https://www.reuters.com/world/asia-pacific/exclusive-russia-...
Doesn't that say something about them not trusting each others currency?
Would you trust the yuan? Chinese people can't exchange to other currencies freely, or transfer money abroad. It's effectively held up by a captive audience (subjugated people).