No need to remove the the rumble motor, if you are careful and gentle and have some good tweezers you can unplug the battery cable after step 4, but it’s safer to do all steps

This is not true, there are 3 options:

1) Replace the stem with telescopic one

2) Add the stem adapter https://www.amazon.com/TranzX-Alloy-Twin...

3) Replace the handlebar with curved one

Yes, it is possible, something like https://www.aliexpress.com/item/Aluminum...

Although the original stem has much better quality, so I ended up just adding this adapter to make the stem longer: https://www.amazon.com/TranzX-Alloy-Twin...

Just FYI: firmware update seems to be possible only by using an Android device, not iOS.