That is truly interesting. The build you have is on my list as a "mystery build". I don't know what features or fixes it provided. I don't even know the associated build number. I only know it existed and the date it was released. I believe It was only the second build released for the H Plus. So yeah, it's pretty out of date. In itself, that's not all that bad. Many folks are still on the very oldest release, and it works perfectly for them.
Newer builds came with issues that ranged from lost features, features almost no one ever used, some firmware defects, camera problems, user limitations. Lots of negatives related to the few gains. However, there was one gain I personally find useful. In build 777, redundant control was added. That means if you loose the normal 2.4Ghz drone control signal, the system automatically engages the backup system through the 5.8Ghz normally used for the camera. I like having that available. Somewhere along the way, provisions were made for using larger SD cards. That's another "positive" some folks actually needed. Build 822 is the current build, and the one I use most of the time. It has all the good stuff, but it did block access to some calibrations that were still available in Build 777. The calibrations don't do much you would ever use, but many folks want full access to everything anyway.
There is nothing wrong with leaving the drone on it's current build until you get a good feel what it does and what it doesn't do. If you do an update, and then have problems, it will make it hard to determine whether it is an update issue, or if the drone actually has a defect. This is your decision. Again, for what it's worth, I left mine on the original build 652 until just a few months ago. Then went to straight to the latest Build 822, and have had no problems with it.
Updates come in two basic varieties:
OTA (Over the air): I'm not sure your current build supports that. It is something else that came along the way somewhere. If it works, you can update to the latest available build using your home WiFi system. Many folks find this method easier, mainly because the instructions are provided on YouTube, and videos are easier to see what is to be done. Downside is you can only update to the current build, and only once, and I don't believe you can go back without doing some other things manually. Another problem is that some controller errors prevent you from uploading the upgrade that you need to resolve the controller error. But that's pretty rare.
SD Cards: In this method, you download the updates to SD cards, and the update is done by inserting the cards in the controller and the camera.
Upside: You can go directly from any build you have loaded, to any other build for which you can find the files. (Some builds vanished into history, and either no longer exist, or only parts of them exist). You can to in either direction, as many times as you like.
Downside: The instructions (the ones you mentioned above). They are in written format, and are in excessive detail. Many look at it, and say "NO WAY!". However, if you struggle your way through the detail, you get a benefit. At some point in the process, you realize what is really being done. A light bulb comes on in your head that says "Man! This is REALLY easy!". And you never use OTA again.