(I hope I am allowed to post links here)

These are some of the bikes near me, that are on or below $300. Which one do you think is suitable for a beginner + would last at least a little bit long + has essential parts?

https://macon.craigslist.org/bik/5408435585.html $100
* https://macon.craigslist.org/bik/5422427467.html $195
https://macon.craigslist.org/bik/5433452640.html $200
https://macon.craigslist.org/bik/5385570550.html $300

*This one looks "complete" and ideal to me, but then again, I'm just a "newb" when it comes to biking.

I am a total beginner with bikes, I never had one as a child; I don't know how to ride one, even as a teenager. I'm sorry if this is a stupid question, but what are those adjustable things near the handle? Also, is riding a "mountain bike" on a smooth road bad?