Can you explain meaning of these lines in -> https://www.geeksforgeeks.org/reverse-a-list-in-groups-of-given-size/

#1 
if (next != NULL)  
head->next = reverse(next, k);  


return prev;
#2

@guptanikhil898 we have to reverse in groups of size k so after reversing a grp just calling on the next grp. its also mentioned in the comment.

#3

specifically, what will be stored in head->next can you please show diagramatically
head->next = reverse(next, k);

#4

@guptanikhil898 recursively call ho raha hai reverse call hota rahega aakhir mein return prev hoga toh pehle head mein prev phir har step pe connect hota rahega ek baar dry run karke dekho chohte input ke liye aajayega samajh