I understand you have several question regarding retailed processor box. See answers below:
1.) The "FPO" (5. line before "E4") is the unique ID/serial of a I5 4570? Remember that the FPO is a batch number, so identifies a batch of processors of the same model; however, is not unique neither the same among processors of the same model number.
The only unique/serial number is the ATPO of the processor.
2.) The FPO number always has 8 alphanumerical characters? That’s correct.
3.I can also find the "FPO"-Number on the paper box? That’s correct. FPO or Batch number is called.
4.) Is there an example image of the seal? No, there is not.
5.) Can I see the "FPO"-Number of the CPU through a window in the sealed box? Yes, you can.
6.) On the paper box is a not removable (only breakable) paper seal? That’s breakable paper seal.
7.) Is there any through a package readable RFID-Chip on or in the Box? No, there is not. Only the information provided on the metal surface.
7.1) If yes, which frequency? 125kHz, 13,56Mhz, 868Mhz, 915Mhz, or...? The processor frequency is 3.2 GHz.