Does this toilet have an automatic lid opening function?

No it doesn't. It comes with the manual lid and seat ring that has silent and slow-down lid closing device

How to turn on/off the automatic flushing function when leaving the seat?

The automatic flushing function is turned on by default. If you need to adjust the settings in special circumstances, please contact customer service

How to flush during a power outage?

Tankless smart toilets are equipped with an emergency battery box that supports flushing during a power outage by pressing a button on the side of the toilet.

What is the SEAT height of this toilet?

The seat height of this toilet is around 17.7 inches.

where is the tank that holds the water for flushing?

The toilet has no tank and is directly connected to the water pipe. Therefore, there are certain requirements for the water pressure and water yield of your house.