Downgrade skype on Android to before Microsoft ruined it I have downloaded a few apk's from APKmirror 

removed skype from my Nexus 5x

adb install -r -d com.skype.raider_7.34.0.114-119668850_minAPI15\(armeabi-v7a\)\(nodpi\)_apkmirror.com.apk 
5486 KB/s (37425319 bytes in 6.661s)
Failure [INSTALL_FAILED_VERSION_DOWNGRADE]


Is there any way to downgrade without error?  I do not like what Microsoft did to skype at all.
You should Uninstall the new version before insalling an old version.

But most companies stop supporting old versions after a major change so it can be possible that after some time MicroSoft decides not to support the version then it will force you to install new version