1.nicotine causes changes in brain structure believed to lead to addiction.
에서 to의 용법이 뭔가요 ??

2.in a four-year study of 1,264 young people, of those who became hooked, one in ten showed signs whithin only tow days of first smoking.
에서 of those who는 소유격 관계대명사 용법으로 쓰인거 맞나요 ????

3. even smokers ofrelatively few cigarettes had withdrawal symptoms when deprived of nicotine.
에서 of 앞에는 명사가 와야 된다는 걸로 알고 있는데 of 앞에 형용사가 와 있네요 ... 왜 of를 쓴거죠 ?

4. the vaccine nicvax stimulates the immune system to make antibiotics that keep nicotine from entering the brain.
에서 to 부정사는 형용사적 용법으로 쓰인거 맞죠???
질문이 좀 많지만 친절한 답변 부탁드리겠습니다 ^^