can the ps4 play playstation, PSP, PS2, PS3
It won't be backwards compatible, but you should still be able to access the games via the cloud once it's available in 2014, and before that many of them will be on PSN Plus as well.
idk we dont have a ps4 yet
No, the whole system is different.
If I'm correct it can play PS3
no, the ps 4 will sadly not be backwards compatible...... fortunately its still better than Xbox one