Do I always get a free save slot that I can load anytime without the 5HG fee for the times that I spend HG during the game? Like on an outgoing call? I was looking online but I didn’t see anything about this. When I bought deep story a save slot that requires no HG to load appeared, saying it’s there for when I spent HG and it loads to the beginning of deep story. 

I was wondering if I could use this feature to create such a save slot after finishing day 4 for each character so that I can load it freely as much as I want and do all the endings. 

Is it possible or am I missing something and there’s a reason why there’s a thing online regarding this?