3 months in china

next week ill be leaving for china (Beijing) to study there for three months! im super excited and extremely anxious but thats beyond the point. i have a list of questions that i would really need answer to:

1. i will need to buy a local sim. which one do i choose? is there anything i should look out for? what will be a reasonable price to pay for it?
2. my phone doesent support nfc. will it be a problem? can i buy a phone there and expect it to fully work when im back?
3. where should i go out to party on my first weekend there?
4. i heard from people that some kind of underground rock or similar genres exist, is that the case? if so where can i find underground concert venues in Beijing?
5. is there a three month ticket for public transportation? i bet there is, but can i make it online in advance?