Question about Xiaomi SmartMi 2S

It looks like only the models sold in China had a battery indicator. However, according to the manufacturer, the SmartMi 2S runs for up to 20 hours (but not at the highest level). So if it is charged overnight, it can certainly provide some cooling the following day without a cable. With such a long runtime, it's not so important to be able to check the battery level. Just plug it back in at night and it's ready again the next day :).

Yes, if you don't use it for 3-7 days, you know the battery level is 0%. Apparently very high standby power consumption. Otherwise a nice quiet fan.

I don't know.