When you use the RPI command : HELP?, if you use default buffer size = 100 lines from Tera Term Pro, you will not see the full RPI command list like below:
In order to see all of the RPI command, you will need to increase the command line buffer size to larger ones such as 1000 like below:
After change the buffer size, please issue the command again and you will get all of the RPI command printed out to the window: