hey buddy, Open ended Mutual fund means you can invest anytime in the respective Mutual Fund as long as the Mutual Fund is active or is not converted into a Closed ended Mutual fund.
When you want to sell (technical term is redeem units) the units you hold in your Mutual fund what you should also be looking out for is the Exit Load, This will depend from fund to fund but commonly found is "Exit Load 1% if units are redeemed / switched-out within 1 year from the date of allotment"
Enjoy Investing.