Searching for "pokemon platinum complete hack" brought me to this thread, with a hack called "Pokemon Perfect Platinum", which fits the description you've given (being able to catch all the pokemon, etc). Since you didn't provide any links, I'm going to assume this is what you were looking for.
Here's a link I found that's supposed to be a pre-patched version of the game *youtube link removed*. Ran it in no$gba and it seems to work fine, at least up through choosing your starter.
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EDIT: Didn't occur to me that the original uploader might consider someone posting their link elsewhere as stealing, my bad. Will reupload in the future.
Last edited by MaslowK; 6th-February-2014 at 19:50.
Reason: removed stolen link and youtube link
"I think that the problem with this video is it is highly derivative of many popular bands within the genre. Although when viewed on its own merits, it does have a deeper groove. However what it has in groove, it lacks in originality. One can't help but be reminded of such bands as Pearl Jam, White Zombie, Suicidal Tendencies and other bands that bear the mantle of so called "Alternative Rock". One is even reminded of Lorie Anderson when she wore curlers. Hehehmhm! This video speaks less to the heart and more to the sphincter. In closing, I think Korn would do well to learn more from -"