Hey! I'm still kind of new to geese, and I've had my African grey pair for 2 years now. I also have an accidental Canada goose whos friendlier than them
1. Geese are the most imprinted of the birds I've raised, but they stay in the true baby imprinted for maybe less than 1 months? 2? Its less or more depending on how big the breed is and their growth rate. It depends on the breed IMO. Once they turn into juvies usually they aren't imprinted at all, but not aggressive, and then they come around and are friendly again once they are adults and get friendlier as they age in my experience.
2.As babies, they are fully dependent on their human who they imprinted on. Once they get their feathers in they are rather independent though, but the friendly breeds come around after they are past being teenagers.
3. From what I know, Imprinted geese no longer have the ability to be wild again or have natural instincts, I mean they'll forage and run away or attack (depends on the breed) dogs, cats, or other things that come too close but they don't truly have those wild instincts anymore. They CANNOT be released after imprinted though
4. As babies babies, not really? 'any period of time' I mean yes, but they cry and cry when left alone especially if they are alone with no other birds. I take my singularly raised babies with me almost everywhere I go in a purse with towels inside of it or a small container with shavings. They can be left alone for a few hours, but they wont be happy about it, once they start to grow up though they'll be more independent.
So, this is very controversial but in my honest opinion, geese and ducks can still thrive if alone BUT only if you have lots of time to spend with them and possibly even get them a diaper so they can come inside. Otherwise, I'd just get them a friend, even if its not the same breed as them (just make sure they are compatible)
Please dont take my answers TOO seriously because I don't know the exacts and have only raised 2 breeds of them and 3 geese, I'm much more experienced with ducks.