I have 1 subject backlog in the 5th sem and all other sem exams are cleared, can I do MBA?

Yes, you can do MBA, but you need to clear within the stipulated time. Like, if you want admission this year 2019, then need to clear the supplementary within august 2019. Else, your admission is liable to be cancelled. The thing is that you need a graduation certificate without any due in subjects

No, you have to clear all the subject first, then only you can get admission for MBA.