You can solve an individual QBank module only once. However, you can always revise the MCQs & explanations from the review page from the individual QBank module.
You have an option to completely reset your QBank (all modules together) and solve it again - See how.
When you come across an MCQ that you might want to read again, save it using the Bookmarks option. Bookmarks is a brilliant way to organize MCQs for revision - See how.
You can also solve the MCQs again by creating a Custom Module. This is particularly useful when you want to revisit all the MCQs that you have marked wrong. Use hashtags to target your weak areas or focus on the high yield MCQs - See how.