Answer to "How to change the mic?"I'm not sure in what order they're counted, but if speakerphone doesn't work, then it's top-back mic, so if you have at least one channel working in videos and can use phone as regular, then both bottom mic's are fine, so I'm guessing both top mics are faulty. Too bad, they're soldered on the motherboard, while bottom mics are easy to replace. Replacing soldered mics would require qualified specialists to do it with the right tools. Especially considering that they're soldered on both sides of the mainboard against each other, so it's quite tricky.
Answer to "Main Camera Blurry All the Time (Nokia Lumia Icon/930)"It would be useful if you could share a sample picture, something with a bit of a distance. Also check if your focus setting isn't in manual mode. then by the way the picture looks we could guess what could go wrong.