An interesting finding was the relative consistency in C% observed for both forward and backward predictions, as evidenced in Figs. and, where the values exhibit only slight variations. In contrast, the N R% showed a marked disparity between forward and backward predictions, as depicted in Figs. and. This significant difference could be attributed to the generally smaller number of molecules involved in backward predictions compared to forward predictions, simplifying the subgraph isomorphism and potentially leading to a higher number of solutions. This observation is further elaborated upon in Table and Table for validation and test set, respectively. These findings highlight the complexities inherent in backward prediction tasks, making them notably more challenging than their forward counterparts.