I have one 4 month old baby, will open air be too loud for him ?

I was not in an outside car, as they call them. I was inside so the outside didn't affect me. So if you are worried about the outside you can get an inside car.

That depends in how protective you are but too me, he should be fine. Just keep the baby away from the sun 🌞

I would say yes.

I don't think so, we were in the Caboose with my 10 month old and he was with me on the top with the window open. We also went and sat on the outside of the caboose with him and he was perfectly fine with the noises of the tracks. He even took a nap on me.