1) Can I take GMAT test date before a week.
Yes you can provided you get a free slot! (you can even schedule a date for tomorrow as far as i know!) And usually you get free slots too.
2) I am not able to give good time to study (max 5hrs), so will doing just GMAT OG
13 will ohelp to score 650-700
I doubt this! As even after doing a LOT of practice people are not able to score a 700. So i will suggest you to spare some quality time if you are really serious about getting a 700. You can check out my post on how to start gmat preparations(link in my signature)
If you are able to go at least those books then there is a chance(not high though!) that you can hit 650-700 WITHOUT practice.
And 5hrs per day on week days and 7-8hrs on weekends is more than enough, provided you do it for at least 3months.
Good Luck for your preparations!
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