Hacking Can DSTWO do these things?

[Isystematic]

play gb ang gbcolor games and play dsiware games such as PvZ?

 

[JPdensetsu]

You will be able to play any Gameboy and Gameboy Colour game as long as you use a GB(C) emulator such as Lameboy.
Concerning DSiWare games, nobody has cracked them (yet) and nobody seems interested to crack it, so no.

 

[nl255]

GB Color games - Yes, with GameYob
DSiWare - No, no flash cart can do that.

 

[Arras]

It might be of note that there's a regular DS cart release of PvZ so you'll be able to play it anyway. DSiware won't work though.