I've followed everything in this link,
http://www.imx6rex.com/software/getting-started/ , wherein we needed to update the network configuration of the board. I do not have the ethernet cable connected as it says it's optional anyways (I also do not have access to our network). After saving the u-bot parameters and restarting the board (as stated in step 8 of the "Getting Started" manual), that's when I first tried the "startx" which was my first issue in this post.
After you posted the link on how to access the peripherals of the rex, I tried to do the "HDMI" part of the guide, which resulted to the same issue of getting stuck at "Loading extension vivext" and also not being able to locate the "dfs.avi" file when trying to play video to the HDMI display.