Yes, there's a folder in the root of the memory stick called 'seplugins' which you place all of your modules (cheat devices and such), then you need to tell the firmware it's there by placing the filename in a txt file called GAME.TXT or VSH.TXT etc (cheat devices obviously go in GAME).
You can then toggle it on/off from recovery.

3.1x downgraders are a way off. First we need an exploit (a security flaw in the official firmware), which we may or may not find any time soon.
(Don't even bother modifying a 1.50 update to say it's like 3.20 or something; it can't be done).

Once we have an exploit, it will typically be user-mode which means the CPU will only accept unsigned code if it doesn't contain any kernel functions (ie ones that could allow us to access Flash0 or downgrade. (Just because we have flash0 access, doesn't mean we can downgrade).
If it's kernel mode, which is less likely (or we manage to exploit the user exploit into letting us use kernel functions), then we can access the flash0 sector of the internal NAND chip and possibly downgrade.

Downgraders are always risky, it mainly just depends what security they have and how crude the exploit is.

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