Can anyone give me any idea on what the deal is with using an older version of Delphi Firemonkey (XE8) on newer...

Can anyone give me any idea on what the deal is with using an older version of Delphi Firemonkey (XE8) on newer macOS systems? For example, I'm using XE8 and things work fine on my iMac with Yosemite, however I'm having app problems on my Mac Mini with High Sierra. Can I install xCode and PAServer on High Sierra and debug to there, or do I need the newest Delphi? (My employer is difficult to get to spend money on upgades).