is it possible to have only one stand alone .exe file and portable

[code_err]

Yes, it is possible. You have to link statically to Qt libraries, MinGW libraries during compilation, also all bitmaps load as resources. But when You link statically to Qt there are some issues related with licence. When you link dynamically (You have in folder with application all those dlls) You can use LGPL licence that will allow You to now show You source code when Your product is commercial. By linking statically You have to either public source code or buy a commercial licence. If You write for Yourself or for internal purposes of Your company it should not make any difference as far as I am aware.