I have XF 1.5.6 and when I purchased the license I did not purchase media gallery add-on. And now I want to have the Media Gallery in my board. Am I still eligible to buy this product and tag it along with my existing XF 1.5.6? If the answer of num 1 is yes, how much would it cost me? How to install this? What is the version of Media Gallery add-on that compatible with my XF 1.5.6 board? Thank you.