1 - Version v20.1C.2 did not handle the fifth level, v20.1C.6 does. For EKD01 there is an update in the testing phase, if you want to try it is in the Master version.
2 - If SW102 is with Tonsheng protocol it does not need to be updated, only the motor needs to be flashed, with the Java configurator version.
3 - It is the same parameter moved to the "Motor setting" section where it is more correct.
"Motor power max (W)" and "Battery current max (A)" overlap, but can have different functions.
"Battery current max (A)" is important to safeguard the battery. The maximum current that the battery can deliver must be set, it depends on the capacity and type of cells. It can also be used to limit the motor current, but it must be lower than the maximum current of the battery.
"Motor power max (W)" is used to limit the motor power. The current limit is calculated and compared with the previous parameter. The lowest value is used.
For example, with a 36V motor, I set 500W and 17A, the current limit with a charged battery is 500W/40V=12.5A, with a discharged battery 500W/29V=17A. Voltage values considering the drop.
With these settings I do not notice any difference in performance between a full battery and a discharged battery.
Be careful though, not all batteries are able to deliver 17A at 29V!
Furthermore, 500W cannot be continuous, the motor overheats.
4 - Regarding EKD01, from your description I understood that pressing the - (minus) button activates Walk assist, if you accidentally also press the Menu (on/off) button, the settings menu is activated.
In this condition, releasing the buttons does not deactivate Walk assist.
To deactivate it, you must exit the settings menu or turn off the display.
Did I understand correctly?
If so, there is nothing that can be done, it is a bug in that display, it should be reported to the manufacturer.