first off
To Reef Central
im still kinda new at this, some of the question ive asked before so maybe i can help u out a little
u dont really need hermits crabs, they are reef safe however, but if you dont provide them with bigger shells in the tank they will attack snails for their snails, but just snail will do work as well
water change only depend on your filtration system or to be safe once a week will be fine
for question do u mean water change during the initial cycle? or after your tank is up and running?
i think that coral should come last, inverts first, fish second and coral last
always remember, if your not testing for the particular element, dont test it, like for instant, if u dont test for calcium, dont dose calcium. but if u want corals, u will need to test for cal, alk, and mag
hopes that helps