That After I've finished story line 1 , can i go back to all those places in story line 1?

um i would rephrase that, i didn't really get it, but if you mean like after you've finished the game you can go to all the places again that's correct. if it's not that then i'm confused :(

It would really help If you were more clear on what your talking about.

After you finish Ch.1, you can go back to the PLACES in CH.2 (all places are accessible in every chapter except for 4), but the missions, etc. from CH.1 won't be there. For instance, there's an potional mission in Luca in Ch.1. However, if you finish Ch.1 before doing that, then you can't do that mission in Ch.2. You can go back to Luca at Ch.2, but can't do that mission.

OK thanks, Vivi that's what I was wondering.

Also, Final Fantasy X-2 does have that wonderful feature called New Game Plus, so if you choose to skip something or do it a certain way in your first game, you can do it again in the new game, or do it differently. If you're just trying to get Mascot, very few missions are required as early as Chapter 1. In fact, the Moonflow is the only location where you can screw up your chances for an Episode Complete as early as Chapter 1.