Then fu*king learn to ask fu*king questions!
My patience is big, but not unlimited.
For ordinary missions I have already answered the question:
There are no hardcoded generation periods, no hardcoded number of possible missions and no hardcoded number of simultaneous missions. There is also nothing hardcoded based on difficulty. There is NOTHING hardcoded in the generation of ordinary missions whatsoever. The mission generation is completely in the hands of the modder using the available features of the mission script.
That's all I have to say.