before buying, I asked them about UPDATE18 offer. who knew what had to be asked about compatibility, and I doubt that he knows what it is
Please check with Steinberg Support EU about whether your Cubase 6 Education version can use the currently discounted 40% offer. Please use the email address of > info@steinberg.de > to confirm whether you can purchase your selected upgrade for you Cubase 6 Education version.
Regards,
Scott
asknet Customer Service
in same day I also call an official steinberg reseller in my country he replied I have no problems, you EDU version will cease to be edu after purchases 
UPDATE
may is help to another owner of edu version
Thank you for contacting Steinberg support!
You have purchased the wrong upgrade. You have ordered an Upgrade from Cubase Artist but you do not own a Cubase Artist licence.
It is not possible to charge already paid money with a new purchase.
I have initiated the refund.
Our shop partners at Asknet will get in touch with you within the next 48 hours.
The available update for your Cubase 6 licence is the following:
Cubase Pro 9.5 Update from Cubase 4 / 5 / 6 / 6.5 €299.00
Products — Music Software & Audio Hardware | Steinberg
Asknet so what was the problem for example to add in the title for users of EDU to Cubase 4 / 5 / 6 / 6.5
I do not blame anyone, I myself hurried though asked a million people before buying ,apparently a CD Artist 6 in my steinberg box made me choose what I chose