Test Version of TI 2017 deletes TI 2016

As far as I am aware this is correct operation.  ATIH 2017 installs into the exact same folder structure as is used by ATIH 2016 (and earlier versions) therefore the act of installing 2017 will overwrite the previous version files.

If you have uninstalled ATIH 2017 then you should download the full installer for 2016 from your Acronis Account and then reinstall this.  If you sign in with your Acronis Account credentials you should be back to the fully licensed version you had before.  You can view your 2016 Serial from your Acronis Account if needed.

I solved the issue,  I restored  the System from a backup only some days old.

My contribution is more a warning to other users.

Nevertheless thanks for your advice.

I've never seen Acronis install as a parallel application side-by-side where you could have say 2015 and 2016 running simulataneously - it's always been an upgrade when you install a newer version and there is no direct downgrade path.  Same behavior as all of the other backup productes i have used and/or tested and I believe this is common behavior in many software applications.  

Glad you were able to restore from a backup though.  Backups are great for exactly this puropse.  I rely on them over try and decide and always take a backup before a major change that might result in negative or unintended behavior.  Just restore the backup and it's like it never happened.  With faster SSD's like the NVME PCIE hard drives, it can be almost as fast to restore an OS from a backup these days as Try & Decide.  

This is definitely by design. While simple disk-imaging does not require this, more complex tasks would do so. If for no other reason than the amount of system resources and the possibiliy of clashes between different versions trying to do a task at the same time.

Ian