Help with dual steppers on y axis and config

Tandem joints for StepConf were added to master only and are limited to the X and Y axes.
github.com/LinuxCNC/linuxcnc/commit/f213...27a402ba6ec66ea54dfc

how i update cnc 2.8.4 to 2.9 can add dual Y axis,
2.8 not working has try many many different forum help example all only error lot and not working newer, and home button not working at pc display, not have homind all axis or homing Y normal XYZ have and work good. but if add dual Y not working. i has write copy joint 3, joint0=X, joint1=Y joint3=Y2, joint4=Z copy same text joint1 and added joint2. not newer has working. and not can use cnc because need first all axis homing, but not can do this because not have homing buttons active and Y homing button has hide somewer not haveat display. only lot come errors to display not do anythink,