Stream rate of MISSION_CURRENT

Question 1.
I am changing rates of streams in the TELEM1 output via extras.txt in the SD card. I would like to change sending rate of MISSION_CURRENT to 1 Hz, but command below is not working.

mavlink stream -d /dev/ttyS1 -s MISSION_CURRENT -r 1

I don’t know what I am doing wrong. I created my own GCS application and I don’t need MISSION_CURRENT message in such a high stream rate.

Question 2.
Where can I find names of messages used in the upper command.
What is _0? What if I set it for example to _1?

Thank you for your responses