If you are looking for a physical valve or lever, then no. They can be manually operated from you sprinkler control panel. The specific instruction for doing this should be with your control panel (control box).
Yes..buy a fresh small can of pvc solvent.
Approximately 4.5 inches, for a standard box, there is room for either a double or triple manifold.
hand tight the solenoid to off position
yes。 orbit should provide flexible tube ， in order to connect valve to old rigde pipe. I use 3/4 heat tube. works well.
We have a brass 3/4" combined vacuum breaker, backflow preventer, check valve install above ground where the supply line comes out of the house, before the copper pipe goes underground to the manifold assembly box. Such a device is required by code in our area. There are several models available through Home Depot (ours is Model # 34-720A).