Hey, Toxic; it's great that you had such success with your garlic - congratulations. It's the one thing I grow that's practically guaranteed. A word about terminology - 'bulb' usually means the whole underground cluster. The individual segments - the bits you cook with - are called cloves.
1. Can I leave the garlic in the ground, for another winter and expect to see it start growing again in the Spring of 2019?
2. Garlic was the only thing in my garden that absolutely no pest bothered... no insects, birds, slugs, ... nothing. Does it have any known pests? Can planting heavy amontnts of it around the garden deter other insects from bothering other vegetables?
3. I'm are pumped that we got 3-4 cloves on each garlic. Over the moon impressed. It was like Christmas in our garden when we started pulling them up... lol. Is there any way to ensure that next years crop produces even more bulbs per plant?
4. Is it true that you can acclimate your bulbs by re-planting them each year?
1. I'm trying this (leaving in the ground) for the first time, just as an experiment. I cut the scapes as usual, but didn't harvest the bulbs. When the leaves died down I cut the stalk (hardneck) down close to ground level. Green shoots are now showing around the stumps. In the past I've also planted whole 4-clove bulbs spaced about 6". It saves space because each clove becomes a bulb - you get more bulbs in about the same space; but as far as I recall they tended to be smaller. Maybe got more lb total per square foot though.
2. I believe garlic can be hit by a disease - a blight? - and like with potatoes it can't be grown again in that ground for a number of years. I haven't seen insects bother with it, but I've had the growing leaves chewed by - cats? It didn't set the plant back much.
3. My regular practice is to re-plant individual cloves about 5 inches apart in September-October. All things being equal (are they ever?) next summer they produce a crop just as good as the one they came from. I'm also starting to grow from 'bulbils' but that's a whole other topic. Bulbils are mini-cloves that form on top if the plant is allowed to flower.
4. It's often said that plants improve by adapting to local conditions if seed is saved and re-planted year after year. I've not observed this with garlic - or convincingly with anything else; but that's just me.
A last observation (after I cut my finger in the kitchen): If you want to do roast garlic in the oven - where you cut the tops off the cluster of cloves & drizzle with oil - hardneck garlic is downright dangerous. That neck is HARD. I may go back to planting some softneck for that reason.
Glad you're having fun there. Do you grow tomatoes? I saw a clip on TV about a chap in Newfoundland who'd just discovered he could grow the Latah variety there, having tried & failed with several other tomatoes. I grow that one here and it's usually the first to fruit.