You still have the right to dump your own games on the PC and use emulators to play them. The result is the same.
the result is the same (although you can get into trouble for one and for the other you don't), but legally it is not.
It also makes sense. First of all downloading ROMs via torrent is not just downloading, but also offering it to other users. Second - anyone seeing that you download the ROM can't know that you already own a physical copy, which means it can get you into trouble. And in my opinion rightfully so.
Also keep in mind that copies on the internet may have been modified in all sorts of ways. Adding a virus/trojan. Cracked in some way, which may make it impossible to complete the game and so on. Incomplete. It makes no sense for anyone who actually owns physical catridges/copies to download them from non-legal places on the internet.
That is incorrect. If the PS4 had full backwards compatibility with PS1/PS2/PS3, they would be selling a lot more games via PSN right now.
PS3 games are already "offered" via PS Now. A rental service with always online DRM. That's way better for Sony than actually selling ownership of those games. Bandwidth is cheap. Sony has already said that "games as a service" is their goal.
Other PS3 games are re-released on PS4 for way higher prices than on PS3-PSN. Sure, better framerate. Higher resolution. But that's basically it. On PC you can get that by just upgrading your hardware. For SD -> HD it sort of made sense (although the reason for that was primarily shitty upscalers). For HD -> better HD, it doesn't.
You know why there are so many re-releases of last-gen games on those current-gen consoles? Because they sell a lot. If those games were simply sold on PSN as regular last-gen titles, they wouldn't make as much profit, because their prices are really low now most of the time and people would also be able to actually buy a physical copy as well of those games.
To be fair at least a few tiny games are cross-buy, which means you will get those in case you bought the digital PS3 version. But with actual hardware BC you would get all of those games including physical copies. And it's still bullshit, because you get nothing in case you bought the physical edition, which is typically more expensive. There would be solutions for this, like for example checking the physical disc and getting you access in that case to the digital versions.