Please help me before I lose my plant.

Ok I hope you can save it...you should recut any rotting or suspected/squishy tips back until you get to no brown or discolored cross section.

Once you get to white on the cross section, clean your tool and recut just below your last cut, maybe 1/8-1/4” down and let it bleed out open to air. Once here, repeat on any other afflicted tips. It’s optional, but I actually do a couple of drops of rubbing alcohol on the open wound and, once dry, I cover it with Saran Wrap and tape it down for healing. You can also just leave it completely open to air and it will heal just fine. The Saran Wrap just makes for a more uniform callous. Hope this helps. Good luck.

-s

After I cut my branch, some get rot all the way down to where branch is split from main tree and eventually fall off from there . I also applied cinnamon powder.

It is unclear to me if your concern is related to the cutting shriveling up or the cut location on the parent plant. If it is related to the cut location on the parent plant...it has been my experience pruning at the end of the growing season can, in certain plants, cause this type of die back. I'm not sure exactly as to the reason but I would assume the plant is going into hibernation and it causes some sort of local dehydration, shock, or disruption causing the plant to wall off the damaged area and possibly sacrifice other branches. Mostly rainbows have done this to me.