The validation of MBBS degree after completion is totally depend on in which country you want to practice. Like In India, the MBBS degree is valid for three years after completion. This means that you must pass the Foreign Medical Graduate Examination (FMGE) within three years of completing your MBBS degree in order to practice medicine in India. If you fail the FMGE, you can reappear for the exam as many times as you need to pass. However, there is a limit of three attempts.
After passing the GMGE, you will be eligible to register with a State Medical Council (SMC) in India. The SMC will issue you a licence to practice medicine in India
The validity of an MBBS degree in other countries may vary. It is important to check with the medical regulatory body in the country where you want to practice medicine to find out the specific requirements.
So before applying anywhere after MBBS, make sure to ensure all the circumstances of that country.