As of 1.3 (the most recent update) you can only get as far as Olmec. The route to get to hell is fully implemented, but the door to get into hell won't open yet. Hell is still unfinished. I'm not sure what the timeline is for the Hell update, but on the mod page here: spelunky.fyi/mods/m/hdmod-demo/ there is a link to the HDMod Discord server at the bottom, you can see patch notes for any updates there and ask questions about the mod as well.