few questions related to vent

few questions about vent. I am in MA:

1. I want to add a vent in my horizontal counter sink drain. Can I use tee to branch a vertical vent or I have to use wye + 45?

2. vent will go up but can i start up but immediately go horizontal few inches and then go up?

3. can I horizontally U turn (the bottom of the U is more than 1 foot) the vent and then go up?

4. Is there any limitation on horizontal length of a vent? can run a vent 20 feet horizontally and then go up again?

5. what's the vent pipe size requirment? 1.5" for bath (what I have now)? 2" for others, 3" or 4" for main stack and entire house?

6. one 2" vent can serve how many fixtures?

7. when add a vent to my 7 feet long counter sink drain, can I add it anywhere less than 5 feet from the sink side or I have to add it immediately after the p-trap?

thanks,

1. it depends on the situation AND the inspector.
2. No.
3. As the question is stated, ABSOLUTELY not.
4. Usually okay
5. Depends on your code and the fixture and.or the fixture load
6. usually more than you have
7. Anywhere within 5' if it is a 2" drain line.