There is a game called the Attack on Titan Tribute game (it runs on unity and has to be played in the browser): http://fenglee.com/game/aog/

If I would like to make it playable in first person and on PS VR with move controllers (with online multiplayer like the original), how should I do it?

Will I have to start from scratch, basically making a whole new game thats just very similar or is it possible that I get all the recources from the developer himself if i reach out to him and explain myself.

Is it very complicated to port such a game on a different platform (PC -> PS4 VR)?

How do I get access to the technology that allows developing for PS VR? What are possible obstacles that could deny me access and how can this be solved?

Is it possible to publish it in the PS store so its available for download? And if so how?

Is most of the things I ask for even possible bc of the (aot) licenses? Is it only possible if its completely noncommercial? Will I have to change names and some aesthetics so it only strongly resembles AoT?

And the most important question: Is this even possible and if not why?

Please consider that im a big noob and excuse my englisch.

Im excited to read the things you all have to say about it!

Just now, bravesttrojan said:

Will I have to start from scratch, basically making a whole new game thats just very similar or is it possible that I get all the recources from the developer himself if i reach out to him and explain myself.

You would have to create your own implementation of the idea yourself with assets you either own or have rights to. Otherwise you can contact the developer directly but I highly doubt anyone would just give away their assets and rights for nothing. Also, what do you have to offer to the developer in terms of being able to mod their game? Do you have a portfolio and a proven track record making games or working on mods?

2 minutes ago, bravesttrojan said:

Is it very complicated to port such a game on a different platform (PC -> PS4 VR)?

This depends on the engine used and the limitations of the device you wish to port to. If the game was made on Unity then it can port to PS VR. See the following: https://unity3d.com/unity/features/multiplatform

8 minutes ago, bravesttrojan said:

How do I get access to the technology that allows developing for PS VR?

You'll need the dev-kit from Sony. I think this link will help: https://partners.playstation.net/

11 minutes ago, bravesttrojan said:

Is it possible to publish it in the PS store so its available for download? And if so how?

You'll be able to publish to the PS Store if you're a partner. Do you have a company registered?

13 minutes ago, bravesttrojan said:

And the most important question: Is this even possible and if not why?

This is only my opinion, but I think you're wasting your time here. Even if the developer allows you to use their assets, what programming and development background do you have? Why would Sony approve you as a developer for their platform? These are some questions to ask yourself. Based on what I can tell you're just looking to modify an existing project but you have not provided any reference to your skill and abilities. It's okay to dream, but you need to be practical. If you couldn't re-create the game from scratch then you're in way over your head.

I would suggest taking smaller steps and learn to code from the ground up, and eventually work towards your goal in making a VR game like the one you're talking about.