Do backlogs and gap years affect college/university application? How many backlogs are acceptable in UK ?

Backlogs or Gap do affect you candidature but it can be backed by the strong profile and personal statement/Statement of Purpose. You need to explain the reason for your backlogs along with backlog certificate mentioning the backlogs and marks obtained in each subjects. If you had any medical issues you can provide medical certificate along with other documents.

Every university has a certain limit of accepting the backlogs. Generally total number of 15 backlogs are accepted in the UK.

Backlogs can be supplemented with other things such as high IETS Score and other. I would also advise you to work on a personal note to explain the reason for your backlogs.

There would be no difficulty in getting a study visa after 8 years gap if you were excellent in your studies and had a solid record before the gap. As soon as you can present your case properly and explain the reasons for a study gap, you should not find it difficult to obtain UK visa approval.

Your study gap might be legitimate for a number of reasons, and you need an honest explanation and documentation from your immigration officer. You can present it to the University and the Immigration if you have some job experience as evidence of your study gap.