Gitner wrote: Which VAG year can I use it for?
What VAG? What do you understand by the abbreviation VAG?
When it comes to devices, VAG and VAS are two different types of devices.
As for the Volkswagen group - the company is called VGP (Volkswagen Group Polska)
The VAS 5054a is used for diagnosis
every type of cars of the VGP group.
Until recently, the service was forced to use VAS5051B for some models of older cars (usually VW trucks). It was an older, completely different (physically) device. It was (as far as I know) about an underdeveloped ODIS program that was created quite recently. Now you don't need to. The websites are officially banned from using the VAS 5051B. There is no update to VAS5051B and you will not diagnose new cars.
The VAS 5054A interface compared to the KKL is like a Mercedes (ok Audi

), for scooters ..
But of course you can wade in crap. De gustibus non disputandum est.
Your money, you decide.