ADCENTER has never been a feature of the MAC versions, try Content Palette instead https://forums.autodesk.com/t5/autocad-for-mac-forum/autocad-mac-design-centre-urgent/m-p/7822347#M3...

MultiLine Attributes have been around for a couple of versions now: did you miss the check box that says MULTIPLE LINES under options? https://knowledge.autodesk.com/support/autocad-for-mac/learn-explore/caas/CloudHelp/cloudhelp/2018/E...