No it will not
No you will not be able to play the games either way. Systems changes on the PS4 allow them more design capability for games and many titles will be released in a downgraded PS3 version. You still will have to have a PS4 to play PS4 games and a PS3 to play PS3 games.
No, the PS4 will only run the games made for the system. But there is a application on PS4 called PlayStation Now which will allow you to play PS3/PS2 games for a price.
Yes, Gaikai allows gamers to play PS1, PS2, and PS3 Games on PS4.
No, the PS4 does not have backward capability and cannot activate (play) PS3 or PS2 games.
In short, no. Sony haven't released any information regarding a PS4 yet, so we can only assume that you cannot. It is highly likely you will be able to play PS3 games on it, that is - if it really comes out.
No
yes!
No and neither console plays the others games
No the PS4 when it comes out will not play PS2 or PS3 games because it has proven to be a unlimited expense filled with great difficulties and problems if not an impossible task
can you play destiny on the ps3 and play with a friend that has destiny for the ps4
No The PS3 can not be changed to have the ability to play PS2 games,. There is no software or hardware you can purchase that with allow a PS3 not designed to Play PS2 games to be able to play them.
They look amazing compared to PS3 games, and I feel like they play a lot better.