1. Ceres\Sid still support nvidia 340 driver but Stable not
2. Ceres feels snappier then Stable at my old PC

Only one piece will be fixed at a time. Fixes will then be transferred into the testing version, currently Freia (equivalent to Debian Forky), but tinkering and trials with Ceres will continue so it will always be unstable.

How then as you can see i cant reinstall anything?
https://dev1galaxy.org/viewtopic.php?pid=60721#p60721

It does seem you reinstalled by "apt remove" then "apt install" it's expected because of dependency tree is expected these issues is kinda common, it's better to use "apt reinstall" and check dependencies before using "apt remove" exactly, will always give you these headaches, try use Testing instead and you can have a better time

What is the right way for update Ceres and how to avoid this problems in the future?

I don't use Ceres, but I have considered using it. If I were using Ceres I would be using using BTRFS, ZFS, or ext4 with LVM, and the reason is snapshots. And along with one of those, I would probably use a utility like sanoid, snapper, or timeshift. With snapshots, one can "roll" the system back to the state it was in before the upgrade that broke it.

This website could also be useful for repairing a broken system: https://snapshot.debian.org/.

One must be extra careful when using it, though, because using Debian repositories with Devuan can cause serious problems. If only a few packages are required, downloading them manually would be the safest approach. Otherwise, apt-pinning will be required to prevent the automatic installation of Debian packages that you are not interested in.

https://forum.siduction.org/index.php?topic=9864.0
https://forum.siduction.org/index.php?topic=9854.0

How then as you can see i cant reinstall anything?

Because you try to install the broken packages until Debian gets updated packages you will be in that situation trying to use apt. Now you can look into the /var/cache/apt/archives directory to see if those broken packages are there at an older version you can install to try and get it working. You would need to use the dpkg pckage to install them manually with a line like dpkg -i /var/cache/apt/archives/xorg_old_version.deb /var/cache/apt/archives/xfonts-scalable_old_version.deb ..... for all the packages it complains about that will not install with the new packages. This stands a chance of getting back to a working graphical system on your machine. If you get this to work then go into your sources.list or devuan.source if using that and change it to follow the testing then you should not end up with this kind of mess again. Your other option is to follow a stable system which will allow you to use it all the time without this junk happening to you.

Always possible if you know the packages required to be be installed to have them used again.

How then as you can see i cant reinstall anything?
https://dev1galaxy.org/viewtopic.php?pid=60721#p60721

why no variants like "roll back" i.e. copy(replace) over my broken healthy files that not affected this bug, is it possible?

Always possible if you know the packages required to be be installed to have them used again. Then you need to stop updating the system or have put them packages on hold to stop them from being updated until new packages arrive that fix the broken mess. Either way it requires someone who knows their way around the system and the pitfalls of using it with the skills to fix it once broken.

i am ask is it fixible or not?

Eventually the bugs in it and the broken packages will be fixed, until then you get to wait for the fixes like everyone else. Running that version of the OS is only for very experienced people who are ready and able to fix these broken things themselves. A re-install of it will result in the same broken state you are in now if you want newer software with less chance of having broken packages and systems then use the testing/Freia branch this is composed of software that is just slightly older by a few days or week or two than the Ceres/unstable but only get into it if no major bugs are found in it while it is being confirmed by people not reporting any in the unstable packages. This allows you to run the newer software with greater likelihood of it being usable most of the time.

Please stop complaing about Ceres is broken.

Thanks,
i am not complain,
i am ask is it fixible or not?

If you want a stable environment use Excalibur. It has some bugs, but it is tested and released for general use.

When you are a bit more daring you may use Testing, which currently is Freia.

Please stop complaing about Ceres is broken.

Why all broken?

Because it is the unstable version of the development branch of Debian being used by it. Which if you took the time to learn about it has breakages all the time. It is not for the faint of heart who want a good working system all the time this is what the stable version is for. The best strategy for running such a system is to not upgrade for days after you see the packages available while you scour the various forums and mailings list to determine what has been broken with the latest updates and if any work a rounds have been found. Especially when you have an nVidia graphics card who drivers always break with just about every new kernel update put out by such a distribution. With such a card you are set for failure on a regular basis using it.