Can I select between Customer Portal ver1.0 and Customer Portal ver2.0?

Sorry. You cannot select GUIs.
GUIs that are provided as of now are as below:

Customer Portal ver2.0 applied Data Centers: only Customer Portal ver2.0 is available
Customer Portal ver2.0 unapplied Data Centers: only Customer Portal ver1.0 is available

Now, Customer Portal ver2.0 will be applied to Data Centers yet to be applied one by one (as of March 2015).