One of our teachers did deliberately go in and answer the first X number of questions wrong (it was either 7 or 10, I can't remember). She then did the rest of the section to the best of her ability and she scored in the 80s (percentile-wise).
I would NOT recommend this as an actual strategy, though. We're experts ("don't try this at home"). :)
Also, the last few questions in a row will not all be experimental questions. The test writers already make sure of this because, otherwise, it would be very unfair to different test takers. If two people both ran out of time with 5 questions to go, but one had 5 experimental questions left and one had 5 "counted" questions left...you can see how the test itself would lose a lot of statistical validity.
As a general rule, answer the questions that you know how to answer in a reasonable amount of time. If you don't know what to do OR it will take you too much time and mental energy to get it, then guess and move on. (Do learn how to make educated guesses, so that you can improve the odds when you do guess.)
Work your way steadily through the section. Don't place extra emphasis on earlier OR later questions - just do what you know how to do and let go when you don't.
Have you read this?
https://www.manhattangmat.com/blog/inde ... lly-tests/If you'd like to delve more deeply into how the scoring works, you can read the Scoring section of our free e-book The GMAT Uncovered (it does get pretty technical - but you might find it interesting). There's already a e-copy waiting for you in your free account on our site.