I would like to give some feedback about the second test "The First": in the side panel it shows that the string being tested is 'abc' while it's another one.

From: http://www.checkio.org/mission/the-longest-palindromic/solve/

HTTP_USER_AGENT:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.87 Safari/537.36