You cannot do the following transactions online if your current address is not in the US.
The NYS Motor Vehicle Dealer and Transporter Regulations (pdf) [1] (CR-78) requires an automobile dealer to use the military residence address on a certificate of sale if the purchaser has no other residence address (see Section 78.11 on page 20).
Note: You do not need to report a temporary change of address to DMV. This includes military addresses.