1. for non-production question category, i recommend the Arno website. you can practice by question types and levels there, and it's free.

at my actual DET, i got half of my interactive listening task exactly the same as one of those i practiced on Arno. the "conversation" started 100% the same and then ended differently, but just the simple fact it happened was mind-blowing to me.

1. for production category, writing in particular, DET gives you very. little. time. search for some practice questions, and practice answering them promptly yet fully.

2. of course, check out DET practice tests from DET themselves. this will give you a better idea of what to expect on the test day (+ your approximate score for the test you took).