Hotels have age restrictions. They don't allow anyone under the age of 18 to rent a room and check in alone. Some don't allow anyone alone under the age of 21.
You might re-think your plans to include an adult.
A possible solution would be for your parents to reserve and pay for the room, and make special arrangements with the hotel management for you to stay there alone. They would have to contact various hotels to find if any would allow this arrangement, and my feeling is that none would. Remember, you're legally a child until you are 18 and hotel managements don't condone children staying alone.
In this day and age there are simply too many dangers for a child alone in a strange city.
You can't legally sign a contract until the age 18. Using a credit card, buying an airline ticket, checking into a hotel, renting a car, etc. all constitute signing a contract.
You also have to be 25 years old to rent a car.
Your best---and easiest----option would be to include one of your parents in your plans.