If Xiaomi is willing to use HarmonyOS, it can certainly upgrade. But at present, Xiaomi is not willing to use HarmonyOS, which of course cannot be upgraded.
Like Android, Hongmeng is open source. Anyone can use it for free. But Xiaomi and other mobile phone manufacturers are not willing to use Hongmeng, we can understand. On the one hand, it is because they are used to Android and are not used to switching to Hongmeng. Second, because they have a huge overseas market, they need Google's GMS to provide support. If they change to Hongmeng and lose Google's GMS support, their mobile phones in overseas markets will become bricks. Huawei's HMS software ecosystem is not as good as Android, and if Xiaomi and other manufacturers use it, they will lose a large number of overseas markets.
No. Can Mi 12x upgrade Hongmeng directly?
No. Xiaomi phones do not support upgrading HarmonyOS for the time being. If you want to protect the battery, it is best to keep the phone battery in a normal range, the battery is not over-discharged and not over-saturated, so that the loss can be minimized. In general, we generally choose to keep the power at 30%-90%, close to 30% can be charged, and 90% can be stopped.