Today, I found one thing that 47/S1A_IW_SLC__1SDV_20180321T223246_20180321T223312_021119_0244B0_3DEE.zip and
47/S1A_IW_SLC__1SDV_20180321T223246_20180321T223312_021119_0244B0_7378.zip have same time but different PDI.
I think maybe them processed by different versions of software.
I question is that which one can i use by using different name?
“The product unique identifier (CCCC) is a hexadecimal string generated by computing CRC-16 on the manifest file using CRC-CCITT.” 
i.e. have a look into the manifest files.
I want to know that what is inputting for CRC-CCITT.
For example, I kwon one is processed in 20180322 and other in 20180517. this information can by name get?
no, you can’t get that from the name. you need to look up the manifest file of each dataset, which has the info encoded in the PUID as text (for where you find them, look e.g here). you can open the manifest file in a text editor.