Thank you for your answers Lefty and Udo. Your posts have given me useful info about Arduino IDE.
It is good to know about how upload works. It is not very "industry standard", but if it works it helps.
Udo, is "undo" working well in Arduino environment. Personally I'll take any version control, if it works, that is: it works without any extra steps.
Implicit versions may be deleted any time in order to preserve space. Implicit versions should not be deleted if they are not older than an hour.
Or some other time, or numbered like save_1, save_2 and so on.