I know it does, I've seen the way to dump and patch kernels for 4.X but PRAGMA hasn't updated his thread to stating support firmwares 4.X and 5.X, it still says 5.X only. That's why I wasn't sure if his files included the proper tools to boot LayeredFS on 4.1.
In terms of warmboot softmods, there is none as 2.3 and 3.0 will have access to the same exploit at the same time. Updating to 3.0 will require a game cartridge, either a physical one or a scene dump that will not be provided here for obvious reasons.
As long as the posts here are all properly answered on a timely basis, that means one less thread for every question which makes GBATemp look less cluttered and more organized. That's the only satisfaction I need. Also, yes backup your NAND. That step should always be the first step whenever playing around with hacks. Better to be safe than sorry.