No, it is powered by a single 9V alkaline battery, which provides over 70 hours of continuous operation.
Yes, but you will need a TRS to TRRS adapter (such as the RODE SC4) and potentially a Lightning or USB-C to 3.5mm dongle depending on your phone model.
The +20dB setting boosts the mic signal so you can turn down your camera's internal gain, which usually has low-quality preamps, resulting in much lower background hiss.
The Rycote Lyre is highly durable and made from a single piece of hard-wearing thermoplastic, making it much less likely to snap or sag than traditional rubber-band mounts.