downloading higher levels changed

If you are having problems downloading higher levels, you need to use a more advanced library - for python one that works is "requests" http://docs.python-requests.org/en/latest/ . I think curl would also work.

Could you be more specific about this for those of us who are not using python? When is the 'higher level' cutoff? Also, in what way did it change specifically?

As someone who has been using C, I don't recall having any problems downloading larger levels. Maybe I've been using the "correct" methods all along, I've been using curl.

On the other hand, when submitting the solution for some puzzles I had to change from GET to POST because the solutions became too large.

EDIT: Hmm, if something changed recently, I don't know anything about that. I haven't been very active with the puzzles since 2013.

If I remember well, some levels in the "puzzle series" require protocol including packing.

At least that was required when downloading pages of those who solved given challenge, but I bet it was in puzzle series as well.