Well.. Just before completing Lonesome road i was given the option to launch a nuke at NCR, Legion, Both, or Neither... I chose to nuke Legion... But after nuking legion a new place to the mojave was added.. Dry Wells was its name.. And i was wondering that if you nuke NCR you will get added area and if you nuked both can you go to both areas??

Yes, the I-15, and yeah you could go to both if you nuke them both up.