Hi!
The Switch 2 finally released today.
To answer your questions:
The Switch 2 it's battery is improved however, without the battery (so only the charger connected) won't turn on the Switch 2. It does need a working battery. As long it can detect the battery, it will turn on when connected to the charger (so this means that with a almost broken battery, the Switch 2 can still turn on).
If you keep the Switch in the docking station for a long time, it still won't be a problem, it's made for this (the same for the Switch 1). However. it's not smart if you let the Switch on the charger for weeks, months or longer. This won't be good for any electronic device (to keep it in the charger for weeks/months). If you want to store it in the dock, then unplug the charger, please.
Tear down is not there yet. This will take some time!