If you've done medical & finger print, means MOI already have your name in the system. If ever you want to resign from your current company,to exit Qatar, you need to get an exit permit being under their sponsorship. 2 years ban will start from the day your visa cancelled or the last day the visa is in effect, which mean 180 days from the exit stamp from the airport.Coming back in Business/visit is not a problem to others, depending how the standing of your new employer.Also if you did the Iris scanning at the airport, there's a possibility that they can track your previous sponsor even though you have change your passport. So check what is best for you to come back quicker, or best try other countries.