I have POLYSCIAS FABIAN I brought form Home Depot bought 3 months back. I moved it a location, which didnt get direct light, although the room gets decent amount of light.
Recently, I noticed the leaves are dying and dropping off. Also, I see the branches are turning black, and have also turned soft, so there is some rot inside already.. Please help me save this plant. please note, I have already removed most of the dead live before taking the pics.

Go to your original post and read my reply.

I split that thread off the old thread since it was a new question.
The thread "Polyscias Fabian" in Houseplants forum

Oops, sorry Sue.

Questions for ankitragarwa:
What direction does the window face?
Are the curtains always closed or open?
How often do you check for moisture?
How do you determine when to water?
How much water do you apply?
Does water come out the bottom?
Have you fertilized it?
What did you use? How much and how often?

Fabian is a touchy plant. The main problem is that they are usually large cuttings with few roots. Try to give it "greenhouse" conditions; very bright light (but not much direct sun), very high humidity (you will need a humidifier), moist but not soggy soil, warm temps (above 75* all the time).
If the big stems are soft or very wrinkled, you have probably lost it.

These "Aralias" often loose whole branches in this way; disappointing but nothing can be done to save them (in my experience). Just cut the branches back at a point where there is good solid green wood.
More sunlight (esp. in winter) may help. BTW, these plants take full sun in the tropics, and usually look great.

Thanks @CalPolygardener
What direction does the window face? - The window now faces is south, earlier it was not facing a window
Are the curtains always closed or open? - The curtains are usually open
How often do you check for moisture? I just poke my finger an inch in the soil and see if it moist.
How do you determine when to water? I generally water once a week, unless the soil is very moist
How much water do you apply? generally 1-2 cups
Does water come out the bottom? Yes
Have you fertilized it? No
What did you use? How much and how often? NA

Now that it's in a brighter window there's a better chance for it to recuperate.
Check those stems and see if they're firm or soft. Especially the ones with droopy leaves.

@CalPolygardener I did check the branch and trunk and they are all mushy I think I have lost this one, still tried to trim down the branches as much as I can and now fingers crossed.

Me too.