virtual company

If there are a group of 10 companies,and one com A is the default DAT (Master) company
and all others are under this company we have created a Virtual Company 1 for
Com B,com C,com D and VC2 for com E,com F,com G Com H
I have two questions here,

1.can the master Company A access data of all the other companies ?

2.How can the Company A access the data of all the other companies?

Thanks in advance for your advise.