Gas light is on but I have full tank (Honda zoomer/ruckus)?

So I got a Honda and today I drove to the gas station before I was driving home. I filled it all up and drove for about 50 minutes when the gas light turned on. I couldn't understand why it did so because I have driven far longer than that without needing gas, so I thought there might be a leak somewhere. So I stopped and checked the tank and it was still a lot of fuel left. I know that the light wasn't supposed to be in when there's so much gas left.

Do you know what could be the reason for why the light is on?

Can I still get purchase a car from a dealership with bad credit?

Want to get a used car that costs 8,000 at the Honda dealership, but my credit score is like 425 (lol yeah i know haha)

But I have a really good job and have for the last year even been paying rent for 7 months and I'm down to put a 5,000 down payment on it. Even though my credit score is bad do you think i'll get approved?

Should I purchase this car?

I'm thinking about buying a 2002 Mitsubishi Eclipse 4 cylinder car. I really love how the car looks and this will be my first car ever buying. I will mostly be using it for commutes from my home to work and maybe 1 long trip a week. My friend mentioned that the car requires special fuel (i385 or something) because its a "racecar". He races cars and is an automotive engineer. This doesn't sound right to me because its a 4 cylinder automatic car and doesn't seem to me like it would need any special fuel. So is he right and is this a reliable car to get, i really don't want to buy an average looking Honda i wanted something that stands out and i really love this car.