My experience and now in china. 12306 cannot work, i dunno why so before coming to China, I used Trip. No problem getting on board the train. Went to the counter to change to earlier train with no problem.
On Alipay and Wechat pay, no problem with alipay in all purchases, metro, train ticket over the counter, mama shop, etc. Wechat pay is giving me problem. Verfiied my account b4 in SG and could see my cc card, etc but when I wanted to pay, it prompted to verify my details again. Submitted passport, my photo, etc.
I used cash when Alipay is not supported but bring more small notes, if u r buying a bottle of water n give the seller 100, he wll either grumble or no notes. 1 troublesome, i am using cimb, most alipay transaction needs otp. delay a lot.