"Suddenly I need to double click instead of single on a sketch or feature to see/change the dimensions."
I assume you mean this is while you aren't in any active sketch or command? If yes, then "Instant 3d" has gotten turned off.
"Also if I draw one line, I need to give the "line" command again to draw another one."
That sounds like the setting indicated below has gotten turned on.
I'm not aware of any way to lock user settings, but you can use the Copy Settings Wizard to save them and reload when needed. See Can I save my SolidWorks settings for when I upgrade, or to share with another user?.
I can't believe I didn't notice that one, but there it is. And even more embarrassing is that I didn't think to open my last saved setting file.