Neuroscientists and AI software engineers, I have some questions.

Before we even reach quantum computing status, I was wondering on an old documentary I watched perhaps a decade ago, it was about a microship that was somewhat connected to rat neurons. (I guess it was illegal to try with human neurons?)

I do not recall how they harvested or created the rat neurons, I assume it was stem cells, I also do not recall how they managed to keep the neurons alive.

Point was however, they managed to grow rat neurons, and connect them to a microship, then somehow managed to get the rat neurons to run a flight simulator. Naturally there was no punishment or reward to it, the rat neurons just kept flying it randomly, it wasn´t specified if it even displayed a curiosity.

I assume the experiment was ran by amateur neurobiologists and software engineers, without much to show for as far as I know.

But one thing was indeed a success, both connecting the neurons to the microchip, and having it interact with a simulation.

My questions are:

How easy is to create human neurons outside the human body?

How hard it is to keep them alive?

How easy it is to connect them to a microchgip or otherwise a computing system?

How easy would be to in turn connect that hybrid system to a human being? And through where? would it be sufficient to connect it to let´s say the nerves in a finger? or would it must absolutely be connected to the brain?

I assume that if said external hybrid sytem is possible, it should have a means to connect to a human being that in turn has a means to connect to it, since I personally doubt there would be a means to naturally connect let´s say, like in the movie Avatar in which they connect their nervious system through a natural connection. I also assume that if one can have a direct biological connection to an outside brain, it would perhaps be permanent or be unable to disconnect from said connection, eventhough in theory could be a whole building full of brain