Answering:
1.1: No, it willnot remove the licence from the other vcenter.
1.2: You can use, but VMware offers you the possibility to go at my.vmware.com and split the license in 2 separate codes to keep compliance. Is an easy step to do and don't take more than a few minutes. KB http://kb.vmware.com/kb/2006972 explains how to do that.
For 2, you can use the same license, but again, you can split the license in 2 to be 100% compliant.
Hope this helps.
Marcelo
@mtsoares42