Because you were confusing two very different things. As I said, the government will decide if and when we can resume playing football and more specifically with crowds. They won't determine when this season is officially ended and next season starts.
It doesn't matter how old the competition is. Finishing the FA Cup this season (or next season) isn't going to save clubs from going bankrupt. Completing League seasons will.
As for how late things can go, it's possible that the window for completing next season is actually smaller than the window for completing this season. I'd guess that providing we're playing by June then we could complete the remainder of this season* and have time to complete next season. You've then probably got a 3 month window where, assuming you intend to complete next season without changes, you'd probably have to scrap the remainder of this season in order to be finished in time for the Euros. However if things dragged on beyond September then it would be very possible that you couldn't complete a full calendar next season regardless of the remainder of this season. In which case you'd probably just finish this season, have a couple of months of exhibition games then go straight into the Euros.
*assuming there's some compromises with how the CL/EL is finished, FA Cup etc.
It doesn't matter how old the competition is. Finishing the FA Cup this season (or next season) isn't going to save clubs from going bankrupt. Completing League seasons will.
As for how late things can go, it's possible that the window for completing next season is actually smaller than the window for completing this season. I'd guess that providing we're playing by June then we could complete the remainder of this season* and have time to complete next season. You've then probably got a 3 month window where, assuming you intend to complete next season without changes, you'd probably have to scrap the remainder of this season in order to be finished in time for the Euros. However if things dragged on beyond September then it would be very possible that you couldn't complete a full calendar next season regardless of the remainder of this season. In which case you'd probably just finish this season, have a couple of months of exhibition games then go straight into the Euros.
*assuming there's some compromises with how the CL/EL is finished, FA Cup etc.