I've never seen you here before, so welcome back.
After I finish answering all the questions, I usually........a quick revision.
Easy as it might seem, but it is causing controversy.
Please note that "easy as it it might seem" is a concessive clause, so you cannot use "but." You can say: Easy as it might seem, it is causing controversy OR It might seem easy, but it is causing controversy.
That said, the answer to your question hinges on whether you are using BrE or AmE. In AmE, "revision" means "change" and collocates with "make" (see (1) here
). However, it arises from the context of your sentence that the speaker does not change but goes over the answers after finishing the test.
In your sentence, "revision" would be "review" in AmE (see (2) in the mentioned reference) and collocates with "do." Therefore, the answer to your question is do, but please note that that sentence will only be said in British English.