softbricked z3c

hi!
first off all thank you all for contributing to this forum, you guys really rule!
i have a problem....
as the title say i softbricked my z3 compact trying to flash MM on it.
i forgot to click the "allow unknown sources" on the phone before he procedure
i know, i`m stupid. my bad
but now when i tried to flash even stock kitkat on it the flashtool errors in one moment sayin "for flashtool unknown sources has to be enabled"
going thru the forum i saw a thread about the usb debugging mode
http://forum.xda-developers.com/show....php?t=2778437

he fixed it with using an older version of flashtool, but when i install an older version it asks to connect by pressing the back button not the volume down to enable flashing mode...
so i have 2 questions...
is there a way to flash without having the unknown sources on?
i installed the adb all-in-one but not successful to implement the command using the terminal
how to enable flashmode by using an older version when i dont have a back button? (its not arc s :) )