The Long Challenge has binary as well as an optimisation problem. The LunchTime has subtask problems. What are the all possible types of problems available on CodeChef?
There are following type of problems on CodeChef:

Binary: You will get complete score for passing all the test data. Either you get the full score or you do not get any score. There is no partial grading in these problems. All CookOff’s and Long Challenges will have such problems. e.g. PRGIFT

Challenge (max/min score): These are typically optimisation problems that can be improved with heuristics. The wrong solutions get a zero score, the best solution (most optimised) gets the maximum score and remaining solutions get a score relative to the best score depending on how they fared compared to the best solution. Every Long Challenge will have one such problem. e.g. INVBINCF

Interactive: These are special kind of problems that makes you interact with the judge by using STDIN and STDOUT.

Interactive Binary: These are binary problems that are interactive in nature. You will find them in some of the the Long Challenges. So far we have had only one Interactive Binary Problem in our contests. e.g. QPOINT

Interactive Challenge (max/min score): These are Challenge problems that are interactive in nature. You will find them in some of the the Long Challenges. e.g. MINESWPR


Partially graded (subtask): These problems have multiple subtasks. You get a partial score on passing each subtask. Each subtask can have multiple test cases. Unless your solution passes all the test cases in a subtask, you will not get the score for that subtask. These problems are usually based on the format that is used at the IOI. The information on the failed test cases will be visible on the solution page for all such problems. You will find them in all our LunchTime contests. We will also be introducing them in the Long Challenges. e.g. TAAND

CodeGolfing: This is a special type of problems where each problem will be judged on the length of the source code where the best solution (i.e the shortest solution) will receive full score and all other solutions will receive a fraction based how close they come to the best solution. Obviously the solution has to pass all the test cases first. We do not have these problems in any contests hosted by CodeChef. However, they appear in the contests hosted by other institutions. e.g. BINGCD
Can I host a contest for multiplechoice questions?