But the NDVI values need to be between -1 and +1 however, the value rendered is between 114085 and 9822.95. These values when scaled to 100000 gives value between:- 1.1 and 0.09. How can these be solved?
Order of operations means your division is occurring first. Put brackets around your addition and subtraction.
(Float(NIR) - Red) / (Float(NIR) + Red)
I dropped the 2nd and last
Float calls as they're not required because the NIR values are already cast to floating point so the whole operation is promoted.