For group 15 hydrides :

Statement A is correct-stability decreases down the group as H-E bond strength decreases.
Statement B is correct-basicity decreases as the central atom becomes less electronegative, making it less willing to share electron pairs.
Statement C is correct-reducing character increases down the group as the hydrides become easier to oxidize.
Statement D is incorrect-boiling points do not consistently increase; is anomalously high due to strong hydrogen bonding, but is lower, and the trend is irregular.

Therefore, A, B & C only are correct.