Am I allow to pay cash for checked bags at the airport?

I'm going from JFK to TPA. I'm riding JetBlue. This is my first time riding alone so I'm gonna check in one of my luggage. Am I allowed to pay cash for the checked bag, or do I have to pay credit card. By "i" I mean my aunt since I'm 15.

Am I allowed to bring a shampoo bottle onto a plane or no?

In 4 days I'm going back to Florida, going on Jetblue. I'm bringing a backpack and a luggage but I'm gonna check in my luggage so I'm just carrying my bag.
Am I allowed to put like a 8 inch shampoo bottle into my backpack (I'm gonna wear my backpack inside the airport).

What time should we arrive at the airport?

Hi, I'm 17, a guy. I'm going out of town on Saturday morning. My family and I technically leave on Friday since we're spending the night at the hotel next to the SFO Airport. Our flight is at 11:42am on Saturday morning, we're going to Mexico. My dad wants to get to the airport around 7:30am, and so do I. When is a reasonable time to get to the airport for a international flight