2) No, 'struct Foo' is in a different namespace from the typedef'ed name. 'typedef struct Foo Foo' is perfectly valid.
3) Yes, absolutely.
4) Not sure what you mean.
Here's a hint: You'll likely miss one of them unless you realize what the algorithm is trying to do. It's an algorithmic error. The other one is findable from looking at the code without context, but the correct fix isn't entirely obvious without realizing the way the code works.
Pretty good, though :)
I think function foo is supposed to insert a new node (n) into the list before node p, but it's not done properly (while n points to p and p points to n, n does not point back to the item before p).
That should be enough for you to figure the last 2 errors, in any case.
n->p = p->p
I don't see the last one - unless foo should be returning n?
prepend(NULL, &something);
if (p != NULL)
p->p = n;
I don't think I'd expect everyone to get every bug without a little bit of prodding in the right direction. Being able to step through the code and show what it's doing to the data structures would be a first step that would make me happy. Recognizing that the data structure looked like it's a linked list, and finding and and fixing a couple of the bugs, and I'd be very happy.