Will LSPDFR work even if i just bought the game and have no mission done of any sort?

No. You need to complete the Story Mode enough for free roam, alternatively, you can download a 100% savegame.

1 hour ago, Cyan said:

No. You need to complete the Story Mode enough for free roam, alternatively, you can download a 100% savegame.

Really? Why is that? 
I've played LSPDFR before completing the story, and since a year now, I play LSPDFR with the story completed. I don't see any differences 😄 
 

2 hours ago, Luce.Benson said:

Really? Why is that? 
I've played LSPDFR before completing the story, and since a year now, I play LSPDFR with the story completed. I don't see any differences 😄 
 

he said complete the story mode enough for FREE ROAM, not complete the story completely

in other works, complete the prologue and first franklin mission first.

22 hours ago, LionKing131975 said:

Will LSPDFR work even if i just bought the game and have no mission done of any sort?

 

I was able to play this mod after 2 or 3 missions.  I personally like to open it up to all 3 characters.  Be aware though, if your last saved character was Trevor then when you play LSPDFR and drive by the Biker Gang Garage in Mirror Park then they will shoot at you.  Since Trevor isn't too friendly with the Bikers.  When playing this mod the game seems to link you to the last character you played in order for it to work.