Your wifi is not supported. Regarding the sound: Make sure to set vol and pcm to 100%.
Thanks for trying and your patients, anyway 
At least we can add a new troubleshooting hint to the handbook, and we found out that the Indian mirror (yes, I can confirm it, and contacted them) has at least one corrupted image.
It’s helpful to know the Indian mirror had a corrupted image. For smoother troubleshooting, after verifying checksums and resolving downloads, if you need to compress large image files during the process, you can use online Image Compressor tool. It’s a reliable tool for maintaining quality while reducing file size.
Here is the one of best image compressor tool.