  Using the HMI/SDO vector magnetic field observations, we studied the relation
of degree of magnetic non-potentiality with the observed flare/CME in active
regions. From a sample of 77 flare/CME cases, we found a general relation that
degree of non-potentiality is positively correlated with the flare strength and
the associated CME speeds. Since the magnetic flux in the flare-ribbon area is
more related to the reconnection, we trace the strong gradient polarity
inversion line (SGPIL), Schrijver's R value manually along the flare-ribbon
extent. Manually detected SGPIL length and R values show higher correlation
with the flare strength and CME speed than the automatically traced values
without flare-ribbon information. It highlights the difficulty of predicting
the flare strength and CME speed a priori from the pre-flare magnetograms used
in flare prediction models. Although the total, potential magnetic energy
proxies show weak positive correlation, the decrease in free energy exhibits
higher correlation (0.56) with the flare strength and CME speed. Moreover, the
eruptive flares have threshold of SGPIL length (31Mm), R value
($1.6\times10^{19}$Mx), free-energy decrease ($2\times10^{31}$erg) compared to
confined ones. In 90\% eruptive flares, the decay-index curve is steeper
reaching $n_{crit}=1.5$ within 42Mm, whereas it is beyond 42Mm in $>70$%
confined flares. While indicating the improved statistics in the predictive
capability of the AR eruptive behavior with the flare-ribbon information, our
study provides threshold magnetic properties for a flare to be eruptive.
