No worries, I've added some answers below.
1. My interview was online, but I'm not sure about next year's format. There was one in total.
2. You're eligible for any college in the university (e.g. I've been allocated to Gonville and Caius).
3. I'm not sure what I'm allowed to say regarding the interview, but they've talked about the subject in their webinars so you should watch them when you have the time. Anyway, they're conducted in February so you've got lots of time to prepare.
4. I'm not sure about this question, but you can ask the CDT directly.
5. I applied during my final year of an MEng degree, and the offer was conditional on me graduating without a specific mark required (as academic performance is taken into account during the offer making process instead).
6. I studied Electronic Engineering, but people join the CDT after a fairly wide variety of undergraduate courses.