opta/tutorials/mac-address: add note for older bootloader versions

Add a note that older bootloader versions don't have the version number stored at this address, and the code of this example will not work and return v255.

Author: Channel59

content/hardware/07.opta/opta-family/opta/tutorials/16.mac-address/content.md

@@ -229,6 +229,8 @@ To upload the code, click the **Verify** button to compile the sketch and check
 
 The code above retrieves information from an Opta™ device, including its MAC address, and prints it to the Arduino IDE's Serial Monitor. The information shown includes the bootloader version and identifier, secure board information, and general board information.
 
+***Please note that there are versions of the Opta™ with bootloader version `<v24`, which do not store the bootloader identifier at `0x80002F0`. Therefore, it will show `v255`, since the memory area is empty.***
+
 ![Opta™ device information shown in the Arduino IDE Serial Monitor.](assets/serial-monitor-1.png)
 
 - The `printOptaSecureInfo()` function checks if the magic number of the `OptaBoardInfo` structure is `0xB5`, indicating that secure information is available. If it is, it prints the secure information to the IDE's Serial Monitor, including the board's functionalities (Ethernet, Wi-Fi®/Bluetooth® capabilities, and RS-485 capabilities), QSPI memory size, board revision, VID, PID, and the MAC address of the Ethernet port. If the board has Wi-Fi®/Bluetooth® capabilities, the function will also print the MAC address of the Wi-Fi®/Bluetooth® module. 
@@ -240,4 +242,4 @@ In this tutorial, we have learned how to retrieve the MAC address(es) of an Opta
 
 ### Next Steps
 
-Now that you know how to retrieve the MAC address of an Opta™ device, have a look at the Opta™ [User Manual](https://docs.arduino.cc/tutorials/opta/user-manual#communication) to learn how to use its connectivity features such as Wi-Fi®, Bluetooth® and Ethernet capabilities.
+Now that you know how to retrieve the MAC address of an Opta™ device, have a look at the Opta™ [User Manual](https://docs.arduino.cc/tutorials/opta/user-manual#communication) to learn how to use its connectivity features such as Wi-Fi®, Bluetooth® and Ethernet capabilities.