I only want to use the phone as a dev tool and I need the android 2.2. What does 'flashed' mean exactly?
I would suggest asking the seller which Android OS version the ROM they flashed is based on.
In short, the phone will still have the Android OS as 'flashing to cricket' is NOT in reference to the ROM or Operating System.
The seller may be referring to moving the phone off of Verizon as the carrier to Cricket, another CDMA mobile carrier in the US. This seems to be a normal process as Cricket does not have the expansive collection of Android compared to that of Verizon Wireless.
Here are a few thread topics explaining this -
Hope that helps!