What is the minimum period for which I need to stay invested? Is there a lock in period? Is there any penalty (exit load) for earlier redemption?

There is no minimum period or lock-in unless you invest in tax-saving schemes. You have the option to withdraw your money at any time. However, we recommend disciplined long term investing for the best returns. You must also consider the impact of capital gains tax at the time of withdrawal.
Some products have loads (i.e. small charge) on premature exit. They do this to be able to optimise your money and earn the best return. In the write-ups given for each fund in the recommendation screen, we mention the load, if any.