Technically yes, you can still invest in Bitcoin. However, its risky and the price is highly volatile. The question becomes do you believe in it as an investment.
A notable one is its scarcity. It has a fixed maximum supply of 21 million tokens that will ever be in circulation. Over time, the primary incentive will be ownership and sales.
No. There is still some time before the world can mine the whole Bitcoin supply. However, the earlier you take action, the better.