RE: Flat battery
Li batteries will tend to completely die if left to fully discharge. If you park it up with zero indicated charge and leave it to self-discharge further, how long before your car turns into a brick? Dunno. But it will happen if you leave it long enough.
One thing is for sure - if you've ever watched videos of Merc diesels being cranked back into life 30 years after being parked up, that just ain't gonna happen* with an EV!!
(*Well, perhaps it might if it used very low activity batteries, such as nickel-iron batteries like the Baker electrics did. Apparently, Jay Leno's Baker electric still has the original batteries!)
One way or the other, it may likely be recoverable, because the battery pack is constructed of individual cell modules that can be removed or placed. How many would actually die after X time I don't know. Keep paying your battery rental and request a replacement!....
The Leaf will start up the HV battery every 5 days and recharge the 12V battery for a few minutes. I do not know if the Renault ZEs do the same but it would seem possible if the Leaf does it.