Some answers!
1) Honestly really the only way to find about this is to ask the university you are planning to go to about what they will accept and what they won't. A lot of states have some form of lower level-equivalency stuff (a lot of freshman/sophomore classes in my state have a "SUN#" where classes with the same one are guaranteed to count for each other), but it ultimately comes down to what the specific college you want to go to will and will not take. If that's your plan then great, but I'm not kidding about contacting the college first. You really don't want to sink lots of money and time into classes and then find out that it doesn't count for anything.
2) Generally (AFAIK) the important thing isn't so much what age you are, but how long it takes you to get through college. Lots of people skip a year or two before going to college and then might take 5 or even 6/7 years, so it's fairly common to see that. On the other hand if you start taking 8+ years to graduate (based on when you started school, not when you "should have") employers might start to wonder about what took you so long. And honestly lots of times you can get a job or internship through the college anyways if you are willing to look, which gets you an in at the company of your choice.
3) First thing I'm gonna say is that colleges tend to overestimate costs, especially for things like room and board. I'd be willing to bet that if you took a close look at their policies you would find that while things like "dorm housing your first year" and "meal plans" are "heavily encouraged", they aren't actually "Required" by the college. I know that my university basically says "you need to be living on campus for your first year", but I know that I and several others I know certainly skipped that. Sure there are advantages to living in the dorms (notably forced friendship making and closer access to what is going on), but I'd take a look into if your college actually requires you to do that (so far I think I've only found like 1-2 colleges that do) or just "heavily suggests" that you do so. Living off campus can probably cut that $9k "estimated cost" by like 50% (maybe more if you are willing to bike/bus in from farther away than right next door to the campus). Additionally most off campus housings will have some form of kitchen available, which lets you make your own meals from scratch and cut that $9k by probably another 30% or so. Similarly $1000 for books and supplies is also kinda ridiculous. Don't buy books through the bookstore, instead get used ones through places like amazon, or maybe even find "free" PDF's on the internet. Wait for professors to actually tell you they are going to use the book; I've had tons of classes that never did, and it's only more prominent in the CS world where many classes don't even use books.
I wouldn't be surprised if that "estimated costs" breakdown for FSU looked a lot more like this:
Tuiton - $4,640
Rent - $500 / 2 (roomamte) = $250 * 8 = $2000
Food - 4.3 weeks * 8 months * 7 days * 3 meals * $5 = $3612
Fees - $1867
Total: $12,119 - Still expensive, but 40% and $8k less than $20k.
Note on out of state: Lots of time out of state tuition costs are gonna be much higher. Many state college out of state tuition costs are often 2x or more as high as their normal ones, and the fact that Florida is lower down on the totem pole for state economies probably isn't going to help your buying power much either.