Playground Etiquette

What are the rules for being at the playground with other kids around?

Today a lot of kids were around and a little girl about five took a really hard fall face first right in front of me. I paused for about 45 seconds to see if someone was coming before I helped her up and tried to calm her down. She fell from about five feet I was generally worried she might have actually hurt herself. I was helping her put her shoe back on when her mom showed up. She grab her daughter glared at me and stomped off.

Another little girl followed my son and I around and asked me for snacks and if I would also push her on the swing. She told me her house had no food only cheese because her mom hadn’t been paid. Again no parents that I could obviously make out. I felt like I couldn’t let her have apples and yogurt because what if she was allergic to dairy? What if she was just making it up and her mom just wanted her to wait for dinner?

Also is it ok the push another persons child on the swing if they just want to swing next to your son? I felt awkward doing it and terrible not. ( I did)

I don’t know ladies these are just two scenarios that happened today. Are there rules of some kind to follow. Like don’t ever push someone else’s kid. Don’t help a kid up unless it’s a broken bone etc.?