Hello,
Unfortunately, to ensure that every user get a working FW for his device, we've been forced to remove any old MiniLab MKII firmwares from our website.
You will not be able to find any older firmware, but I can eventually give it to you personally. Please PM me to do so.
Note that, the MiniLab MKII firmware extension have been changed recently, and you will not be able to update using the last MCC.
You will need an older MCC in older to downgrade you MiniLab to an older version.
To answer the second question, the C++ programming language was used, but I wonder how it could help you to know it.
Last but not least, I strongly recommand you not to downgrade the device, even if I have to agree, the blinking octave feature was cool.
Have a great day !