Alright, I can't say for touch only screens as I've only used keypad only versions but the way to dump all the memory is to power up the unit; after the test 32 (or maybe 33) which is the keyboard test, press and hold the lower leftmost and upper rightmost keys simultaneously. Eventually you will get a message telling you hoe much memory the unit has and everything will be wiped clean (just the application, no the firmware).
I did have to do it a couple times to get it to work (maybe I wasn't hitting the keys close enought thgether?)
If you don't wait until after the keyboard test, you get an error that a key is stuck and no erasing takes place.
The thing in my application that locked up the PV 1000 (DH+) was that I had a reference to a variable in an alarm message. (Don't remember the type of reference). Panelbuilder verified everything OK but when the PV would reset after download I'd get an error number (sorry, don't remember that either) and the whole thing would be locked up.
Maybe someone else will chime in on how to dump the application on a touch only screen.