DS DSi and DSiWare Titles playable on 3DS with CFW

As you should know by now, Game Boy Advanced games can be played with at least three public "CFW"s (Custom FirmWare)
https://gbatemp.net/threads/pasta-cfw-a-cfw-that-allows-unsigned-cia-to-be-installed-on-old-and-new-3ds-required-ninjhax.388925/
https://gbatemp.net/threads/release-pbt-cfw-import-cias-on-your-sysnand.383242/
and palantine 's CFW (which is a slightly modified release of Govanify 's CFW ( which was actually Yellows8 's (http://3dbrew.org/wiki/User_talk:Yellows8 ) original work)
https://gbatemp.net/threads/4-x-only-cia-cfw-complete-guide.373532/

But what you might have missed is that DS DSi and DSiWare Titles are also playable with a modified patch to the LGY (Legacy) Firm and checksum correction[for the modified patche(s)]

http://3dbrew.org/w/index.php?title=Legacy_FIRM_PXI&diff=next&oldid=11888

Legacy FIRM PXI
This page describes the PXI commands for TWL_FIRM/AGB_FIRM.
Command Header	Available since system version	Description
0x0001....	1.0.0-0	?
0x00020080	1.0.0-0	(u64 application_titleID) This launches the specified TWL title.
0x00030080	1.0.0-0	(u64 application_titleID) This launches the specified GBA VC title.
0x00040080	1.0.0-0	Process9 will eventually wait for the ARM11 to send this command, see here. The command input parameters are not used.
0x0005....	1.0.0-0	?
0x0006....	1.0.0-0	?
0x0007....	1.0.0-0	?
0x0008....	1.0.0-0	?
0x0009....	1.0.0-0	?
0x000A....	1.0.0-0	?
0x000B0040	1.0.0-0	This is used for TWL initialization, prior to using command 0x00020080.
0x000C0800	1.0.0-0	This writes the input 0x80-byte ASCII data to nand:/rw/sys/lgy.log.
[edit]Command 0x2

This does the following:
Waits for an u8 state field to become non-zero.
Clears DSi memory, etc.
Loads the DS(i) application specified by the command request titleID. If this fails, it immediately returns the error for this.
Initializes the DSi memory at 0x02fe7000 and 0x02fffc00.
Loads the TWL launcher located at physical address 0x27C00000, which was written there by the TwlBg ARM11 process.
Loads the TWL bootloader, see here.
Initializes DSi memory/keys, 0x10018000 registers, etc.
Writes value 0x3 to REG_BOOTENV, and value 0x1 to an u8 state field.
Uses svcSignalEvent, then returns.