PlayStation NOW, available to select Samsung Smart TVs (trophies, online multiplayer, and cloud saves support) : r/PS4
Sony: PS3 and PS4 cross-play is 'technically possible' (update) - Polygon
Can You Play PS3 Games on a PS4?
How to Play PS3 Games on the PS4 (with Pictures) - wikiHow
Can a PS5 Play PS3 and PS4 Games? Yes, Mostly
PS4 backwards compatibility: Can You Play PS1, PS2, and PS3 Games on PS4?
LittleBigPlanet 3 servers come back online for PS4, but PS3 and PS Vita game servers to be shut down | TheSixthAxis
Sony has made it nearly impossible to buy PS3 games online | Tom's Guide
Why can't I play Demon's Souls on Ps4 when it's a ps3 greatest hits? Aren't all the greatest hits playable on ps plus? And why is there a remake for the PS5
Guide on How to Play DVD on PS4 Without Internet
How to Play PS2 & PS3 Games on PS4 - Tech Advisor
PS4 backwards compatibility: Can You Play PS1, PS2, and PS3 Games on PS4?
PC/PS4/PS3 CrossPlay Now Available In DC Universe Online; Here's How It Works