My question is that as i have the rc4 version working ,can i just ftp upgrade to rc7?
After that i am gone have problem with the license key (i have to back it up)?
If you have lisensed rc4 installation, just upload packages from rc7 to this box and reboot the system.
I thing that the system package with the other packages must be the same.
Or just upload the OSrc7 to box and reboot?
You can copy system packages with other packages, or x86 package which contains all necessary packages.
If there is RB500, than you have to download and copy one routeros-500 package.
Ok i get that.Just copy the files or the RB500 file (with packages) to board and then reboot.
Then we have to activate once more the new version???
Or is working fine.
No you do not need any activisation.
Download, there will be one package routeros-rb500,
Copy it to Router FTP, reboot your router.
That’s all. 
OK thanks