In the context of developing a machine learning model for a classification problem involving time series data, your team has achieved an AUC ROC value of 99% on the training data with minimal experimentation. While this result is promising, the team is concerned about potential overfitting and data leakage. Beyond exploring advanced algorithms and hyperparameter tuning, what additional steps should be prioritized to ensure the model's robustness and generalizability to unseen data? (Choose two correct options)