Gardasil 4 was equally effective against HPV6 as Gardasil 9.

The HPV tests were designed primarily for use in women and not formally approved (e.g. by FDA) for use in men. Many labs have developed their own tests, but without regulatory approval their reliability cannot be guaranteed. Mostly the results probably are reliable, but it's difficult to know for sure. In any case, a negative result never rules out HPV:  infected people can have negative results. (For example, if you had an infection involving only a surface not contacted by the swab specimens.) And if positive, usually there's nothing to be done -- no need to inform partners, and no need nor benefit from professional exam or to prevent later problems of significance. So there's really no point in testing, in the opinion of most experts. This is a bit controversial -- some experts may be in favor of testing. Anyway, don't be surprised if you have a positive result. Since over half of adults your age have positive results, it is statistically likely your genital and perhaps oral test will reveal HPV. But most likely it will mean nothing important from a health standpoint.

Gardasil-9 is perfectly fine in people previously immunized with Gardasil-4 and often administered to them, if cost is not an issue (around $500, not covered by al health insurance plans). It would protect you against 5 more types, and bring your overall HPV protection from ~70% (the 4 types in Gardasil-4) to about 90%. (But no protection against any types with which you have already been infected.)

 As you likely know, each question includes two follow-up comments/questions and replies, so you have one more coming -- and we don't accept repeated questions on the same topic or exposure, so this is your last question about these issues. Therefore, I recommend holding off on further questions or concerns until you have your HPV test result, in case you would like my comments or advice about it.