Well, then you only need to replace the current SailfishOS r3 with r4, right? Here's one way of doing it, altough there are many possibilities:get the filesystem image, for example vgrade-sailfish_r4.tar.bz2 unpack the archive with bunzip2 to get the tar archive vgrade-sailfish_r4.tar (or if using windows use 7-zip or whatever similar tool?) copy the tarfile image somewhere on your N9, for example to your MyDocs/ go to Harmattan console, and go to root with "devel-su" mount your ALT_OS partition with command "mount /dev/mmcblk0p4 /mnt" (now I am assuming your ALT_OS is partition 4...) check that you have the correct partition mounted: "ls -l /mnt" (you should see the SailfishOS partition, I assume you know what it looks like) delete all files from there with command "rm -rf /mnt" check again with command "ls -l /mnt", it should be empty now untar the new r4 files there with command "tar -xvf /home/user/MyDocs/vgrade-sailfish_r4.tar --numeric-owner -C /mnt" check that all is in order there with "ls -l /mnt" sync and umount; "sync ; umount /mnt"