“…There are various methods such fixed point, variational methods, critical point theory, Morse theory and the mountain-pass theorem. For background and recent results, we refer the reader to [1,2,3,4,5,6,7,8,12,13,19,20,22,23,24,26,27,28,29,30,32,33]. For example, Henderson and Thompson investigated existence multiple solutions for second order discrete boundary value problems in [19].…”