1. According to the MTR webpage, in Hong Kong, you take Island, Tsuen Wan, Kwun Tong, and then East Rail Lines to Lok Ma Chau. The trip needs 66 minutes.
I think use Cross Harbour bus service to Hong Hom may use similar time.
Then, you take Shenzhen Metro Line 4 to Shenzhen North Station. The trip needs 21 minutes.
2. No, until 2016, or the time when Hong Kong side opens.