I tried holding the 'Options' key when opening Safari but it makes no difference.
I am aware I can switch to full screen mode after opening, much as I can resize the screen by dragging the corner.
I am wanting Safari to open, occupying the whole screen (rather than "full screen") when first opening, as in fact it was doing before.
Default open to "full screen" would be an improvement on the current situation though.
All I know is that something has changed and I have to resize the screen every time I open Safari.
As I said in my post, the only instructions I can find to reset default screen size is to resize the screen then close and then reopen using the "Reopen Last Closed Tab" command under the 'History' drop down menu.
Unfortunately this is NOT Working.
It just reopens Safari with the same reduced screen size.
Am I the only person to ever have this problem?