If you start moving when the device is turned on a screen will pop up asking if you want to start the timer. Once underway, however, it's up to the rider to restart the timer if you stop the timer for any reason. I think this is a reasonable implementation. I have both Garmin and OSM maps. Both work just fine; I was having an unrelated issue which is what prompted me to unnecessarily buy the Garmin maps.

There are some settings required in order to get proper turn-by-turn directions when using a TCX file; Garmin's manual is terrible in this regard.