does quantity of ads effects CPC?. I heard if I will place all thress ad unit and one link unit, it will hurt my CPC
Yes, but also depend on where do you place your ads at. Less ads you get higher CPC. More ads, you get lower CPC but higher chance people will click it since its everywhere.
The highest paying ads are listed in the first unit you have on the page. It's often been my experience that I'll get more $$$ and a higher CTR with one really placed ad on the page. All sites are different though. See what works best for you.
Just to clarify what has been said. Having more ad units on you page will lower average CPC. You average CPC will go down, but that is because you will have more clicks, and some of the clicks will be lower paying than if you had fewer units. Usually more ads means higher revenue, but lower average CPC.