Buy Cubase 10 Pro update 08.2021

I am the owner of a fairly old Mac mini.
The last possible system to be installed is 10.13.6.
The last version I have is Cubase 8 Pro.
I would like to buy an update to the latest version supported by my computer, i.e. Cubase
10 Pro. (The newer one won’t go). How to do it?
Will Cubase 7.5 work after updating the USB key?
I once had a situation where after updating the Cubase 6 key, Cubase SX3 stopped working and I could not open projects made in it.
Best wishes

Steinberg only sells the latest version of Cubase, not older versions. But that license will allow you run older versions like 10 or 7.5. The Download Assistant currently has versions back to 9.5 available and Steinberg support can send you links to older versions if needed.

The other option besides buying a C11 license is to find someone selling an old version of C10. Buyer beware comes into play with this option.

Thank you for your answer.