Several questions about the battery you most want to know

——The battery says 3.7v, but people keep saying that it is 4.2v really. Why?——

A fully charged secondary is 4.2v. People use the nominal (think average) voltage as the generic battery voltage. 3.6v is the actual nominal voltage of most ICR. Most IMR are around 3.8v. Nominal voltage is calculated by taking a fully charged battery at 4.2v, depleting it at 0.5c until it is at 3.0v and plotting the average voltage. I expect that 3.7v is a number fluff to look better on the wrapper of ICRs and keep up with those manufacturers whose battery has a low enough internal resistance to actual have a nominal voltage of 3.7v.