Who's still developing non-smart TV's?
Almost all of them?
I believe your basic assumption is flawed. I'm assuming you're defining a "smart TV" as one that has installable/hackable software or at least some type of Internet connection. A quick search shows that there are still many, many TVs being developed and produced that have none of this; just a nice ...
Have you considered Vizio TV's? I am not sure if they are available in your country but they would fulfill all your requirements and you might even come in under your budget!
You could most definitely get a 50" FHD (or 1080p) Vizio television for ~$800, but you may also be able to get an M-Series Vizio, this being their 4K model, for around $800.
If you want a modern TV without all the perceived smart-TV risk, just buy any TV with the features you want and disable the Internet and wireless settings.
Boom, instant non-smart TV.
I had a cutting-edge (for the time) 60" Sharp Aquos four-color 240fps 3D full HDTV for over a year before I turned the Internet on. I just had no use for it (at the time). ...
Yes this feature is offered, as for a remote option, I'm not sure.
I owned a Panasonic Viera TC-65AX800U, which was purchased in 2014. It was a 65" 4K LED model. This option was located in a separate "Format" sub-menu, not the main picture options menu (contrast, brightness, etc). I've owned many TV's over the last 10 years or so, and this is the only ...
Price: can only speak from where I live, but it seems from your comment that it is alittle over budget.
Screen size: 43, 50, 55
Resolution: full hd
SmartTv: Yes, android, nuff said?
Refresh rate: 100Hz with 800Hz motionflow
Response time: 10-15 ms (Do not have any source on this, but this is stated from Sony who visited our store.)...
Like @mbmast says in the comments, it might be more logical to have a full AV Receiver. That is the device that is meant to do this.
But as for a TV, I think that the 2017 Visio P55-E1 ticks most, if not all, your requirements:
Depending on how much you want to spend I would say Raspberry Pi would be the way to go as you will be able to install a nice OS that could be tailored to what you are after, or if you would farther have a slightly easier system there are a number of Zotac mini PC’s that pack a lot of hardware in a tiny form factor.
As for the controller if you have a look ...
I own a Samsung JU6050 which offers this feature.
However it does not have a button on the remote, but maybe I just don't know it has. This TV also offers smart features like youtube, which makes this option quite usable. However in my opinion the menu reacts quite slow, but it never crashed or so. It just needs some time.
Maybe the higher end models of ...
I have a 55' Samsung Q6FN. It's a QLED TV. It has everything you listed except for 3D.
The current model is the Q70R. It costs around 1.2k USD.
Check out the RTINGS review for this TV.