That's too bad. The TL3 is an overall good eReader in my opinion, but of course buying electronics second-hand always poses the risk of getting a malfunctioning device. :/
And about ADE: Yep, the Pocketbook firmware can directly read Adobe ACSM files and download the ebook without going through ADE. But if you're using Linux and ever need to run ADE for some reason, this guide still works:
https://wiki.mobileread.com/wiki/ADE_2.01_Linux