Not sure I get the question: Definitely, there's drinking water in Ouranopoli (and plenty if places to buy soft & less soft drinks). If you mean Mount Athos proper, there ic plenty of watering-spots and springs around. One's supposed to spend the nights at the monastries' guest spaces, not to camp around (the visit schedule has to be submitted beforenhand; one may camp- if allowed to- up on the peak of Mount Athos. Not sure about water up there).

For two years in a stretch you'd most probably need a residence permit. The wisest thing is to check with an embassy.

this office ia for pilgrims going to the HOLY MOUNT ATHOS. .this is nt the place you newd for a two year stay in Greece....females are not permited to go to Agio OROS. male monks live there

Many weeks in advance. This is a must. Contact the Pilgrim Bureau by phone or email. There are English speakers. Acquiring the permit as far in advance as possible, esp if not Orthodox. Also make boat reservations in advance. Even in Nov. the boat was sold out with a long waiting list. If you plan to stay over night contact the specific monasteries in advance. The mount Athos pilgrims Bureau has all the info. Enjoy, worth the trip.

It is always possible to visit Mount Athos and stay the night in one of the Orthodox monasteries. However, you will need to apply for a visa in advance, which you can collect at the Pilgrim's Office in Ouranoupoli. Further, non-orthodox visitors can stay three nights, whereas orthodox pilgrims are allowed to stay much longer (10 days, I thought).