Is this a pre-owned system? If it is, then this could be an incomplete downgrade done by a previous owner, and you would have no way to know. This would explain a 9.9+ browser being present, along with memchunkhax failing (it doesn't run on firms 9.3+, but lower firmwares can boot higher firms just fine.)
If this is the case, then there are two possibilities. If the browser opens on a black screen that immediately gives an error asking you to update, you have a dummy browser, and you can forget about using the browser right now. If it waits until you attempt to load a web page before giving you the error, then you might
be able to bypass the update error by doing the following:
- Goto System Settings. Then change the datetime to January 1, 2000, 00:00.
- Use the browser 'Initialize savedata' option, before any page gets loaded triggering the browser-version message.
- Continue to use browserhax as normal.
- Note that you must not press the HOME button to return from the browser normally, otherwise you will have to reinitialize the savedata again. Once the datetime reaches January 2, you will have to repeat these steps if you want to continue using this bypass.
This is not guaranteed to work, because 10.7 browser patches this bypass exploit. So if you happen to have a 10.7+ browser installed, this won't work (note: 10.7 browser is version 1.7625 in NA region, not sure about EU.)
Also, check your system settings. If you see a nintendo network id settings button, then you're kinda out of luck on that end as well, because it means you have system settings app 7.x or higher. I'm not entirely sure if higher versions of system settings that included the nintendo network id settings button would work fine on 6.2 though, so this may be unlikely.
this is all the case, then you don't have many options beyond updating to latest fw and using Seedminer, if you can even successfully do a system update, or using ntrboot. Or, it is possible that you could do a cart update to a fw 9.0-11.3, and maybe the homebrew launcher method would work better. Unsure if this would work, in the event that you had a 11.4+ firm installed, the cart might not downgrade it back to 9.0-11.3 and then you wouldn't be able to use the homebrew launcher entry points, because they rely on exploits present in 11.3 firm and lower to run.
Or, if this is a pre-owned system... check to make sure it's not already modded.