Help for switching from T2(G) to T2(G)

Hi,

I have a few questions about changing employment. If someone can help me out, I really appreciate. Many thanks!

Background
I'm currently holding Tier2 General visa in a small company. I obtained this T2 in last November. A few days ago, I just got an offer from a big company which is also my dream company. But I'm quite worried about the visa thing.

Question
1. The COS I used for the T2 general is corresponding to a manager position. However, the new job is a graduate scheme in the same field. Is there any impact on the T2 re-application because of this kind of down grade job title?

2. I remember when I applied for my current T2 visa, I've read a term in the T2 guidance, which is when changing the employment, the current employer should withdraw the COS from home office first, then the new employer will be able to allocate a new COS. Is this true? Because I can't find this term any more in the website.

Thank you very much!

Please, someone can help me out? Many thanks