The Ace3DS+ can use two kernels:
- ACE Wood firmware V1.62
- AOS V2.13
ACE Wood firmware V1.62 Details:
This kernel is actually just an unofficial and modified version of Wood R4 (v1.62) that supports microSD cards ranging between 2GB-32GB by normal means (64GB+ using special formatting software). If you were around to see the glory days of Wood RPG/Wood R4 then you'd know right off the bat this kernel is a really good kernel. The only drawback is the fact that this specific version doesn't support RTS (Real Time Saving) features like the more modern, popular, and official Wood R4 flashcart, the R4i Gold 3DS Plus (which also runs the same version essentially, just extra features rendering the 1.64 version).
AOS V2.13 Details:
The AOS kernel merely stands for Ace3DS Operating System, and is essentially the exact same kernel as above, however this one has an extra feature that allows you to boot into emulators directly from the menu of the kernel, rather than hunting down the emulators in the Wood R4 menu like normal. This doesn't provide any edges or extra performance over the kernel above, it functions the same, still lacks RTS features, over all, it's just the same kernel. The emulation functions of this kernel does NOT include anything special, in fact what it does is it looks for the emulators you downloaded and put on your SD card, then when you select one of the emulators, it will then launch the emulator. The results will be the exact same if you launched it with any other flashcart kernel, this means that emulation performance and game compatibility does NOT change, it's exactly the same.
Conclusion:
Both of these kernels are the exact same, one just has the ability to launch emulators directly from the kernel menu rather than you having to manually find the emulator yourself on your flashcart.
Updates for the kernels:
Updates for Wood R4 haven't been done since 2013, however the kernel doesn't really need updates when 99.8% of the games work on it already (the other .2% being games we either don't know or have or likely shovelware titles people likely didn't know existed). If you really wanted to update the kernel then you'd have to have the source code or SDK of said kernel and some knowledge on the flashcart hardware at hand to actually do anything on it. None of which is publicly available, however nobody is stopping your from disassembling it yourself and creating a new source to work with for the public, though I recommend not doing it with this unofficial version of Wood R4, I would go straight to the official version so you get the right content.
Updates to the flashcart flash (aka firmware):
None are needed because these flashcarts work on any firmware of the DSi or 3DS systems, with or without custom firmware.