Usually when new generators come out, Sony finds out quick and patches it to block them from working.
To answer your question, they work if you use them as soon as there released.
PS. I am not advising you to do so. Purchasing from store is way better.
+trust???
There'd be a few things to check first - Was the code generated for the right region? Codes generated for a US version of the game, will not work for a European. - Was the code generated specifically for Explorers of Sky? Time/Darkness codes might not necessarily work. - Are you sure the code is genuine, and has been typed correctly by the person who gave it to you? One of those is bound to be the problem.
RING COUNTER as opposed to grey codes
You can modify a mission for one here: http://apointlessplace.net/wms/wmgenerate.html Most of the codes generated work.
The only codes that existed for Spiral Knights are unique Item Redeeming codes, generated for special events. You wouldn't be able to randomly guess one; they item for the code would have to be generated first, and they don't do that until they need to, and codes can only be used once.
The password (generated from internal DS data) is unique to each DS and passwords from other people will not work on your DS
There are no codes in clash of clans.
they are randomly generated for each game. you can find the codes in besaid and you first have to examine them.
Redeem codes are unique, and can only be used once. The Item you receive from them is generated for that purpose only, so guessing a code won't work, because the item for the code won't have been generated yet.
The password (generated from internal DS data) is unique to each DS and passwords from other people will not work on your DS
I can only assume you are looking for universal remote control codes. Such codes are generated by the universal remote manufacturer rather than the TV manufacturer. As such, the actual codes will differ from one remote to another. Regretfully, Olevia TV's (for the most part) use proprietary infrared frequencies. This means that the code for another TV brand will not work with Olevia TV's.
it is probably randomly generated.
There are diamond codes that work, but they are not cheat codes. You would have to get them from a site that is working with Disney for a promotion. These codes only work once.