A:AnswerYes. Also, for use in churches and at military funerals, should you be at one, there is a setting to mute the annoying DING it makes. It's not accessed through the dial on top like my other Canon that has a little person shushing for silent mode, but it can be found with some fiddling around.
A:AnswerI don't thin the battery will last more than 15 minutes. So the camera would shut down on low battery. Only other limit would be the size of your memory card. I have a 64 GB card and it can take over an hour of video. But the battery, left unattended, won't. I have not heard of an external power source you could use to mimic the battery.
A:AnswerI have a 128 Gb SD card in my SX720. It was recommended by the sales staff if you were taking a lot of movies on a trip. I don't know what the upper limit is on SD capacity