In last few decades, the concept of functions with non-decreasing increments got attention of many mathematicians due to its worth and importance. We would like to establish a connection/relation among functions with non-decreasing increments and arithmetic integral mean, Wright convex functions, convex functions, r?convex functions, Jensen m?convex functions, m?convex functions, m ? r?convex functions, k?monotonic functions, absolutely monotonic functions, completely monotonic functions, Laplace Transform and exponentially convex functions, by using thenite di erence operator as di erent cases ofm h f. We also consider function with nondecreasing increments of third order and get the generalisations of the Levinson''stype inequality and Jensen-Mercer''s-type inequality by using Jensen-Boas inequality. We will deduce some general identities of Popoviciu type for discrete case for sums for function and sequence in two dimension using higher order r divided difference, positivity of these expressions are characterised for higher order r?convex functions. We will also obtain some general identities of Popoviciu type for integral R R P(y; z)f(y; z)dy dz of higher order di erentiable function and positivity of these expressions are characterised for higher order r?convex and completely monotonic functions. We would discuss some applications in terms of generalised Cauchy-type means and exponential convexity as well. We would get the generalisation of discrete identity and inequality ofCeby sev-type and discuss generalisation of integral identities and inequalities ofCeby sev-type and K. Fan-type for higher order r?convex functions with two variables. Further, we will obtain double weighted integrals Montgomery''s identities and using these identities we deduce generalisation of Ostrowski- and Gr uss-type inequalities for double weighted integrals for di erentiable functions of higher order with two variables.