First time traveling alone...

To Seoul. Actually anywhere, for that matter. I just have a few questions for anyone who can help me.

1. AirBnB vs hotel vs hostel/guest house (which is recommended)
2. Why do you recommend that?
3. Are there many things to do alone or should I start meeting people to hang out with now?
4. I ordered a Korean language book to help me study some useful phrases, any apps you like that you would recommend to further assist in learning basics?

Any other tips would be greatly appreciated! 😊