Erasing chip after Level 2 protection

Hi,

  I am testing a Nucleo-64 stmL07xxx board and playing around with the protection parts.  After I added my application I set Level 2 protection to prevent read/erase and program of processor. It says its irreversable, but I thought it meant irreversable if you also wanted the code to still exist in flash. I thought erasing the chip (like in other micorcontrollers) would simply totally erase the chip , but am I wrong thinking this (and have to replace the chip)?  If this is the case , then it looks like I should use a Level 1 protection to prevent parts of memory from being overwritten ?

Thanks

Scott