Can I play GTA5 just on the computer without any ps3?

It would require emulator to do that. Unfortunately, most of the PS3 emulator on the internet is virus file. Some real PS3 emulator exist but problem is if you running game of PS3 emulator it would be laggy and buggy.

I can help you, give me 20 min and I'll be back.

When the PC version is released yes.

Just buy the PC version due later in the year.

Not really I mean it's possible, but would be difficult to deal with .

Not yet. The PC version comes out in the fall.

There's no PS3 emulator that's capable of playing actual games.