Does "Mnoho" require the genitive? Ergo, the difference between Mám mhono sestry and Mám mnoho sester?
Yes, it requires genitive. The same with málo, hodně etc. Mám mnoho sestry is incorrect.
So "sester" is genitive plural of "sestra"? And why is it like that? Is it an irregular? I haven't found any rule regarding such case