To correctly understand the relationship between the two historical periods before and after the reform and opening up, we can start from the following aspects: correctly treat the historical chronology, comprehensively grasp the internal logic of the changes of the times, comparatively study the differences and connections between the two periods, highlight the historical significance of the reform and opening up, and grasp the new stage of Socialism with Chinese characteristics's development.

1. Correctly treat the historical chronology: the two historical periods before and after the reform and opening up are important chronologies of China's social and historical development, and we need to correctly treat the historical process and turning point.

2. Fully grasp the internal logic of the changes of the times: the changes before and after the reform and opening up are the embodiment of the law of historical development and need to be comprehensively grasped from the aspects of economy, politics and culture.

3. Comparative study of differences and connections before and after: Comparative study of differences and connections before and after will help us better understand the historical background and influence of reform and opening up.

4. Highlight the historical significance of reform and opening up: Reform and opening up is a great period in the history of China, highlighting its great historical significance in economic development and cultural exchanges.

5. Grasp the new stage of Socialism with Chinese characteristics's development: After the reform and opening up, Socialism with Chinese characteristics has entered a new stage of development, which requires continuous innovation and improvement in theory and practice.