Swim meets for a clueless newbie

I am thinking of participating a swim meet, just to experience it once in my life. I had a lot of reservations about signing up for a meet. But after reading some of the threads in the forums, my fears have subsided. 1. I can't do flip turns very well. It seems I can do open turns instead. 2. I fear my goggles will pop off during my dive. Looks like I can start in the water which I am more comfortable with anyways. But there are a few things that I'm still wondering about. 1. I'm pretty slow. I've read somewhere that most meets have a "slow heat"? What does that mean really? So you could have multiple people being #1 for the same age group? And how can you tell if a meet has several heats? 2. Why is it when I view some of the past event results, some events have rankings for the top 3 swimmers and some have only 1? I am attaching a screenshot of what I am talking about. Does that mean there was only 1 person swimming in that event? 3. How does one finish off for freestyle? Do you have to press a buzzer?