Zul Hijjah

Q: Does the virtue of worship etc. in the first 10 days of Zul Hijjah also include Eidhul Adhaa? i.e. there is great reward for worship on the day of Eid too? 

I'm aware Eid is the 10th, but I haven't heard anyone saying Eid is also included in the blessed 10 days, and hence should be taken advantage of too.

Q: Will a person be sinful if they cut their hair or nails during the first 10 days of Zul Hijjah if they are making qurbaani?

Q: Is it true that praying four rakat of nafil on the first of Zil Hijjah give the reward of 25 years praying?