each running instance has their own SystemID and needs a separate license. But you can use the CHR without licene in FREE mode, it works with all functions
Well yes and no
Each CHR license level as different built-in rate limiting (to encourage user testing and then to later purchase a CHR license).
CHR Free mode works but tops out at around 1-meg for bi-directional Ethernet throughput.
CHR License level P1 has a 1-Gig Speed-Limit
CHR Licence level P10 has a 10-Gig Speed-Limit
CHR License level P-Unlimited has no built-in Speed-Limits
CHR License level "60-day trial" has no built-in Speed-Limits but only runs for 60 days
For more CHR License Level info , take a look at: https://wiki.mikrotik.com/wiki/Manual:CHR#CHR_Licensing
If you are going to use a paid-for CHR License in a production enviornment, I would only suggest the License Level P-Unlimited.
Note - it is pretty easy to transfer/move a license from one CHR to a different CHR. This can come in pretty if you happen to crash a box and end up building a new CHR.