When a baby became juvenile and adult?
Depends on how often you are feeding them and many other factors. I would say the division between baby and juvenile is arbitrary, but you can mark the transition to adulthood by sexual maturity. Males can reach sexual maturity as small as 400g, which can take under a year, but become fully mature closer to around 700-800g (about 18 months, again depending on multiple factors. Females take longer. While they may achieve sexual maturity near 1000g, maybe even less, it is ill advised to breed them at that size. 1500g is the generally accepted suggestion and this takes 2-3 years from birth. So, under most circumstances, 18-36 months to reach adulthood as a whole. That’s how I see it.
I don’t believe this is steadfast and always true, but it gives an idea.
All of the above, but I would add. They are ready when they are ready.
The right numbers wont always produce offspring. The female knows best.