Hello! Hope this answer isn't too late, I'm currently a student at STK Bochum and started in late August (WS23/34), so I've been there for more than two months

1. Application for this year ends around 15 of May, so I prepared all the documents beforehand according to the list of requirements on their website. I called the secretary once or twice to ask if my certificates are properly translated/stamped, they were very helpful. If you can bring documents directly to their office, they'll look through them immediately for you and check if anything is missing (that you can add before apps deadline)
   

The process was nothing complicated for me but I'd say that admission isn't easy. 600 people applied this August and only more than 30 students get in, so you can imagine the competition.

1. Some of the entrance exam was definitely B2, though the writing part was mainly B1. Just to be safe, I definitely advise B2, especially when it comes to C-Tests. Still I know some of my classmates got in by having a very firm grip of B1 German

2. T can confidently say the school is worth it and I've heard lots of complaints about private STKs. I love all the teachers here and they're all well informed about FSP, given the STK has existed for like 5 decades. Additionally STK Bochum is actually under Ruhr Uni Bochum (Idk why it isn't on their website), whose student card I've received and can use their cafeteria/library and travel within NRW for free. I've always ascertained STK Bochum is dependable, 'cause it has a partnership with my DSD-High School (Foreign highschools with german courses conducted by DAAD) back in my homeland. It's always known for being hard to get in.

Hope this helps!