Hi and welcome @panda ! Learning how to do cardio/endurance exercise with T1 is tricky but very doable. Here’s a thread documenting my experiments with fueling for running. Lots of data on doses and timing here:
On 1 and 2: For short to medium distance runs I was preloading with fast-acting carbs (Transcend, glucose tabs) and supplementing with the same as needed during activity. I learned about how far my BG would drop for various intensities and distances, and fueled on that basis. I wouldn’t wait for alerts to fuel: there’s usually a lag with CGMs, especially when dehydrated or when BG is moving fast. I carried a wrist-mounted glucometer that @Eric constructed for me–invaluable for getting immediate point values. I strongly recommend collecting all these numbers for yourself. You’ll quickly get a sense of how your own body’s dynamics work in different conditions.
On 3: Post run it just depended on where I landed. Be sure to eat something, though, to replace the muscle glucose you used up.
On 4: For emergencies a Transcend or two will help you out of many holes, but if you’re especially low and far from possible assistance I’d add some other more substantial fuels that work over longer durations. For longer workouts I’d also consider a mix of fast and slower acting carbs.
Anyway, that’s off the top of my head. Lots of folks in the forum will chime in with other helpful information, I’m sure.