Which firmware version is fitted now
One software number has several versions. The VIN shows them in a list: the current one is marked, with newer and older ones beside it. You can download only a version whose file is in the database.
A version is not a different number
0AM300065G 6560 and 0AM300065G 6562 are one software number and two versions. 0AM and 0CW are different software. You do not pick a version across those.
Do you have to fit the newest
No. A recovery often uses the version that was on the unit. The newest line in the list does not mean it can be written to a different software number.
Where you see it
In the VIN result on the homepage. In the catalog you can add the version after the number, with a space.
Where to do this
A firmware file from the catalog or by VIN costs 20 €. Immo Off together with the VIN change costs 30 €. The download button appears after payment and a copy is sent by email. If that version is not in the database, there is no button. Before writing, match the software number and version to the unit label.
Short answers
Is the current version always in the database?
No. Then there is no download button.
Can I fit an older one?
Only within the same software number, and only if you mean to change the version on your unit.
Who marks the current one?
The VIN search result for that car.