1) Only concrete or cinder blocks/bricks contain my raspberries, otherwise they spread freely. You might be able to get by sealing just the 12 inches closest to the fenceline, while leaving a gap for drainage and deeper root penetration, but not 100% sure. Berries and redwoods have to be some of the toughest root situations around, not certain I'd trust only rocky soil or wood as a barrier to them. You never want to damage the neighboring redwood tree roots or leave them exposed to sunlight too long during digging in any case -- you can accidentally trigger them into sprouting on your side of the property!

2) Yes.
3) Box stores and some nurseries have them right now.