RE: New owner's questions
Welcome to the Forum!
How did you manage to 'own' the battery? Renault don't sell them, and can be disabled remotely if the payments are not forthcoming!
As to your questions - why would you want to 'coast'? It provides no benefit and would disengage any possibility of regeneration and claiming some of the spent energy. You are not using electricity pressing the accelerator, just cancelling or reducing the regen. To see this, switch the display to show power output and you'll see what I mean.
There's no way you can usefully flatten the battery, if totally flat, it will not charge at all. NiCads of acertain age did benefit from this stretching, but not now. Renault's advice in the manual is sound - top up when you can, there is no requirement for further conditioning.