on which version of Android Auto can I use all third-party apps?
Taking your question strictly, not possible with any version of Android Auto
First, an app must be built with the framework for Android Auto, and most apps (by default) are not built that way
For that reason you have to use an app like Screen2Auto - you will run Screen2Auto over AA, and inside the Screen2Auto you will open YouTube, EMail, Playstore, etc - then Screen2Auto will project those 'third party' apps to the Infotainment display (aka Head unit), or informally to the AA
Alternatively, you could use Fermata player to play from YouTube service. For Fermata you don't need Screen2Auto because Fermata is built for AA, hence you can directly run Fermata from AA.
Or, instead of Fermata, you could use CarTube to play from the YT service, but CarTube will not allow you to play while the car is running (only when engine is switched off)
Although the mentioned apps like Screen2Auto, Fermata and CarTube are built for AA, AA have them on the 'blocked' list - and that is why you need the hacks to prevent AA to remove them
Finally, even through Screen2Auto you cannot play Netflix - but that's because of DRM restrictions
Taking your question strictly word by word, the answer is negative (not possible to play all apps over the AA, no matter which AA version you use)
But for that reason you have the hacks like Screen2Auto, Fermata, CarTube - take a search on XDA to find the corresponding threads and to read where to download those apps, how to install, configure and use them
Finally, back to the AA version. I have AA v7.4.620964 (few weeks ago when I was installing, it was the latest available AA version) and I successfully use Screen2Auto Fermata and CarTube with - and that way, I can watch from YT or even write mails on the (AA) Infotainment screen. Hence vaguely and imprecisely speaking, by your words, " I can run (all) third party apps on AA (with that AA version)"
Some details how I installed and applied the hacks (info otherwise scattered around the various XDA threads), about my phone, ROM, root:
https://forum.xda-developers.com/t/...g-only-for-root-devices.4062787/post-86771647