In the future, the most challenging issue for network operators will be to provide survivability against failure and enhance resource utilization simultaneously in spectrally-spatially elastic optical networks (SS-EONs). To address the above issue, this letter, for the first time, proposes a shared backup path protection-based resource allocation model considering inter-core and inter-mode crosstalks (XTs) for offline SS-EONs. The proposed model introduces two optimization problems as integer linear programming (ILP), which are based on XT-avoided and XT-aware resource allocation, to minimize the highest utilized spectrum slot index. Heuristic approaches are introduced for a network where ILP is not tractable.