Hi!

As my new Jolla hopefully arriving soon, I am planning to give my current Nokia N9 to my daughter.

My N9 has several tweaks on it and it is so time consuming to restore every tweak when re-flashing is needed.

Therefore, it would be good if I could make a full storage image backup and in case daughter later messes something up (and most likely she will as she is only 7,5 years old) - just restore phone from the backup image.

Any advice on making making such full backup and restoring it to the phone?

Thanks in advance!

It's been covered before, either you use backupmenu or use ubiboot to .tar your partitions so that you can restore them later...

Got a good deal and purchased another Nokia N9 64gb.

Is it ok to make such full backup of one Nokia N9 64gb and to restore this backup to another Nokia N9 64gb? What would be better/easier to use for that purpose only? Uniboot or backupmenu?

It's your own choice of course
Backupmenu is maybe easier for people with less skills as it is somewhat automated. Ubiboot just provides a console and tools for you to do it manually but it places no restrictions whatsoever to you.

I have been reading about Backupmenu and Uniboot. In order to use them, Linux computer is required. Is there any simple solution for Windows computer?

You can use ubiboot to make a full backup also on windows, as you can tar the /home and /root partitions and store the tarfiles on MyDocs partition (if you have space enough there, it takes maximum 6GB for the tarfiles if your filesystems are full...)
As the MyDocs partition is normally formatted as FAT you can then mount it on windows...