Yeah, using older versions of the toolchain is a terrible idea for all sorts of reasons. If everyone digs their heels in and doesn't update their stuff after a certain point, suddenly every project will need a different toolchain and/or a different set of libs to compile. And that's no bueno.
It's already addressed that this would be impossible, but I just want to further point out that if you had access to Decrypt9 then you would have zero need of downgrading in the first place.
You don't. A system transfer by definition involves overwriting everything on the target system. However, you can use save managers like JKSM to back up and preserve savegames, and any legitimate games that you've purchased are still tied to your NNID, so you'll be able to redownload them when...
Yeah, I would expect that the other system does get all its data overwritten. So it might be worth using JKSM to back up any save data that you might care about preserving.
You have Luma3DS and arm9loaderhax already? THEN WHY DIDN'T YOU SAY SO? All you ever said was that your console is on 9.2. A "console on 9.2" is a COMPLETELY different thing from "a console that has arm9loaderhax installed." You have to give all relevant information in order for people to help...
Apparently he has two consoles. Console A is an o3ds on 9.2. Console B is another 3ds on 11.0. He wants to use the dsiware method to mod console B and wants to know how to use console A to accomplish this.
The answer is that he needs to mod console A, then use it to mod console B.
auto
Then...
This is the page that tells you how to do the DSIware transfer thing:
https://github.com/Plailect/Guide/wiki/DSiWare-Downgrade
However, you cannot actually do the DSIware transfer thing until you have fully modded your 9.2 console, which you can accomplish by following the directions here...
What you should do is just follow the guide for the console that you're using right now. Get it fully modded. Then after that, you'll be able to do the dsiware/system transfer trick to start modding your second console.
If you don't actually care about modding *this* console and are only using it as a method of delivering dsiwarehax to a second console, then you can simply update this one to 11.0.
EDIT: Nah, disregard that. Misread the situation
Both the hardmod and dsiware methods involve making a nand backup as part of the process, so the OP would have to make one regardless of which he chooses.
Yeah. You just want to be absolutely sure to use the "keep a9lh" function when flashing the emunand to sysnand. Then you'll wanna change your cfw's options to boot into sysnand instead of emunand.
Considering you have arm9loaderhax, the easiest thing to do would be to stop having two NANDs. Simply flash your emunand to sysnand (with the "keep a9lh" option in Decrypt9) and off you go.
Also, you aren't supposed to patch AGB_FIRM if you're using Luma. The cfw does that for you automatically.