You should have mentioned the same in your CV also and the employer is not okay with it, they will reject your application and then the question of joining and subsequent background verification will not arise. On the other hand if you have received the appointment order, then background verification will be done for the documents concerned with experience only. Moreover, Distance learning is also a degree awarded by a University and that is at par with any regular degree. Of course, some companies take people holding regular degree; some even take from reputed colleges, B Schools etc but such companies will show it in their employment criteria that degree from tier A colleges..etc.