MechaPwn VS mechadump

As per the MechaPwn GitHub page, you can use it on:

MechaPwn can make your PS2 region-free via softmodding. More people should know about it. It doesn't work on the launch model PS2 though.

Mechapwn does exactly that but without needing a modchip.

These days it's best not to use a mod chip as there are better methods available, one such method is mechapwn which patches disc protections in software, it has a few limitations that mod chips don't have such as requiring the discs to be Master patched (if not using Force unlock) or if you enable force unlock you won't be able to use CDs or PS1 games.

You can but there's a missing step. Certain model PS2s can make use of something called MechaPwn. However, in order to run MechaPwn (which is homebrew), you would need a way to run homebrew -- which is what Free MC Boot or Free DVD Boot is for.

And also remember that on your model, you can also apply mechapwn if you want to run psx games. More info in https://github.com/MechaResearch/MechaPwn

If you're looking to play PAL games on an NTSC PS2 and don't mind soft modding your console, check mechapwn to see if your console is eligible: https://github.com/MechaResearch/MechaPwn

The Japanese PS2 has both English and Japanese options available in the OSD by default. On versions later than Deckard slims you can change the OSD Region with Mechapwn and unlock other region specific languages.

Basically code execution was achieved on the mechacon processor of later model PS2s, this processor among many other things handles security stuff. There's some writeup-ish GitHub readmes and you can also glean some info from this PCSX2 pull request (unfortunately they didn't like it).