1. Will i be able to enter other GCC country in next 2 months if i get job offer?
You will be able to enter another GCC country but you cant have a Work visa there without cancelling the Qatar Work Visa, if your new employer in another GCC country wishes then you can have both the Work visa paying extra money to the immigration,
but I understood that you don't need Qatar visa anymore.

2. Does my RP get cancelled automatically in all the records of Qatar after 6 months?
If you stay more than 06 months out of the country while the RP is valid, then you can't enter to the country with the same RP,do not misunderstand that RP will be cancelled, unless it is stamped by the immigration saying cancelled it wont cancell for 02 years from the date of your exit from Qatar. yes after 02 years all the records will be deleted and you can enter to Qatar without No objection letter from the previous employer.

3. Is it necessary to get cancelled stamp on visa to enter again in Qatar or any other GCC country?
It necessary to get Cancelled stamped if you are joining with a new employer in Qatar within 02 years, also to get another GCC RP, better you get it stamped for safer side.

4. Is there any ban to enter Qatar or any other GCC nations if i leave Qatar without cancelling Visa?
If you don't cancell the visa or cancelled the visa, if you do not have the No objection letter the ban is 02 years to Qatar.

Read more: http://www.qatarliving.com/answers/visas-and-permits/visa-cancellation-1...