First, you need an image with
the size of 42x29 and in .png
format. And rename it to 'i.png'
Then use
X-plore(see Downloads section) to extract all contents of Opera Mini 4.2, 2.06 installer.
After that, look for 'i.png' and replace it with your icon.
Lastly, zip all the contents using X-plore then rename the extension from .zip to .jar