The EndrrGDPS (GDPS = Geometry Dash Private Server) was created and is currently maintained by Endrr. The GDPS has integrated IAD for mobile. You can find the GDPS on his discord server. Click this for a how-to on the gdps installation. Here is what the GDPS has to offer:
The Demon List is created by Skyavoxii. The list shows the top 10 hardest rated levels in the GDPS. Please note that the list may be outdated due to being no longer maintained. You can find the demon list here.
The Challenge List is also created by Skyavoxii. The list shows the hardest verified challenges in the GDPS. Find it here.
Website created by WYNDSTALKER.