I googled about cheat codes for DoS and I instantly found Action Replay codes.
http://news.softpedia.com/news/Castlevania-Dawn-of-Sorrow-Action-Replay-Codes-DS-72805.shtml
but I couldn't understand how to use it (on desmume). Also, I don't know how can I understand the code, but I guessed it and converted some of the codes into memory address + byte sequence form. I paste them here as a reminder for me.
Have All Weapons
020F71E0: (byte sequence)
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
99 99 99 99 99 99 99 09
Have All Armors
020F7208: (byte sequence)
99 99 99 99 99 99 99 99
99 99 99 99 99 99 99
Have All Accessories
020F7218: (byte sequence)
99 99 99 99 99 99 99 99
99 99 99 99 99 99 99
Have All Items
020F71BC: (byte sequence)
99 99 99 99
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
99 09
Enemy Database Complete (100% Soul)
020F70D0: (byte sequence)
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
99 99 99 99 99 99 99 00 00 00 90 99 99 99 99 99
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99
020F7150: (byte sequence)
FF FF FF FF FF FF FF FF FF FF FF FF FF FF 0F
Some of these addresses might be useful when you perform SG.
Magic Seal
020F7254: 1F
Edit: pastes the current attempt quietly:
sm7404244. I'm still at Balore though, for some reasons...