1. Nobody knows; it is the prerogative of the medical officer to decide whether you need a full checkup or just a redo of the ECG.
2. Nobody knows; it is up to the medical officer to decide (based on your new checkup results) on what your PES status will be.
If it is just a common test or something, just ask the medical officer for a letter or MC to certify that you were at CMPB for a medical checkup. Your school should accept it.