Gst on plot booking. plz advise.

If you are registered under GST, then GST is levied on sale or advance receipt whichever is earlier. That means:
GST is applicable on advance receipt on plot booking.
GST is applicable on advance receipt on flat booking.

And can you give more clarity on transfer charges, holding charges, admin charges?

Any advance received on furtherance of business GST is payable on that.
If you are a builder then advance received on flat booking or plot of land is subject to payment Of GST on advanced received.

In case you receive advance against sale of your house / flat and you are registered in some other business other than builder no need to pay GST on advance.