Answer:
3. Plants, microbes, animals, and organic matter are the biotic components of the cycle.
4. Soil, water, and N2 gas are the abiotic components of the cycle.
5. The atmosphere is the main reservoir of nitrogen.
6. The nitrogen turns into ammonia.
7. Plants use nitrogen in the form of nitrate.
8. In short terms, nitrogen is essential for all life.
Note: I'm not sure how big of an explanation you're supposed to give in your answers, so these are just shortly worded answers.