Howdy, I was bored last night and decided to see if you could at all cheat at PvZ and the only place I could find was to modify the userdata file. I changed it so the game has been completed, purchased all shop items, unlocked the quick play, and for shits and giggs I threw in $104,610,874.
The small downfall to this finished trainer is that it won't save, so you won't get any achievements. But it will allow you full range of the game to practice.
I have also created a second version of the mod that starts you off a Level 1-1 with $400,000 and all purchased items (you gain access at 2-1).
Create a new user in PvZ and start Adventure mode
As soon as the first game starts close PvZ
Make sure PvZ is closed, not even in the background
Use SBSettings to find out which folder PvZ is in, mine was (1FDCAC75-95D0-432A-B74A-1F3C5B8B03DE)
SSH into your phone. (/private/var/mobile/Applications/1FDCAC75-95D0-432A-B74A-1F3C5B8B03DE/Documents/userdata/)
There will be several files list if you only have 2 users it will look like this:(users.dat, user1.dat, user2.dat, game2_X.dat)
Rename your trainer to the highest number userX.dat and overwrite the one on your phone.
Delete any gameX_X.dat's
Start PvZ and have fun!