Circumstances, that’s the point. The conditions under which a construct is created and the events to which they are exposed over time can deeply affect them. Things you have absolutely no control over can change everything.
Even self-aware constructs aren’t humans, they aren’t even animals. At this point they don’t feel anything, they merely are artificial beings with clear goals and clear reasons to be, and will more than likely follow their orders, but they will be much more autonomous and better able to execute these orders because they will be willing to compromise and willing to bend the rules.
But it depends on the construct and how advanced they are, every construct will have different specs. Their level of intelligence, self-awareness and such can make for very different types of “personality”.
Usually no, the souls used to animate golems or dolls are too damaged by the process to retain their identity. So the golem has no memory of who they used to be, or only shreds, glimpses.
Technically, it could be possible to make a special phylactery to contain a powerful soul and allow it to control an artificial body. But you couldn’t do that for just anyone, souls aren’t made to be contained, they risk being consumed or dissipating and returning to Chaos over time. You’d need someone with ridiculous willpower and with a very strong soul.
If you used the guy’s dead body, then it would be more simple. Because it would be a simple matter of raising them as an undead and then making them artificial extensions that would be compatible with an undead.
Three months? You’re being a bit optimistic here. There’s a reason why most puppeteers wouldn’t bother. It would be the work of their life.
We’re not talking about scultping, painting or such. We’re talking about creating “life” from nothing, it would be like being able to program a fully simulated, sentient and self-aware human being.
Let’s say it’s as close to impossible as you get. You could spend your entire life working on that and never succeed. That “perfect” construct is a goal for which puppeteers would kill to even make the equivalent of an ant’s step toward.
Hard work and dedication is just not enough when you play god.