I recently got a chained shiny Pokemon yesterday and a random shiny today, and I feared that my save file could randomly corrupt, and I could never get it back. I don't use cheat codes, but is it still possible that a saved game on Pokemon Platinum may randomly stop working?
Not "randomly", no. Below are some reasons the save data may become corrupted. If you don't want to read it all, tl;dr: if you want to be maximally safe, don't use cheats, don't use unofficial software, and treat your cartridge well.
Using cheat codes. Cheat codes are direct modifications to the RAM (i.e. live memory) of the game, some of which is written into your save file when you save the game. If the cheat code creates bad data and this is written into your save file, then the game may consider it "corrupt" when you try to load it again. A well-made cheat is safe and will not have side-effects -- but unless you made the cheat and understand exactly what it does (and how the game will handle it), you cannot guarantee any cheat will not have unexpected effects. If you see a "Bad Egg" after using cheats, then your Pokemon's data failed a checksum somewhere -- be careful.
Glitches. Similar to cheat codes, glitches can cause memory alterations that were not anticipated by the developers of the game, and therefore will not be handled by the game when it tries to read your save data. Fortunately, the most famous glitches are well-researched and documented, so you can find out whether a glitch you've used (deliberately or not) poses a risk to your data.
Save editing software. The games use checksums for every section of the save data to validate that it has not been altered between each "legitimate" save. This means that save file editors must be able to accurately re-calculate and re-write the checksum for any data that it changes. While most editing software is watertight in this respect, this process is still prone to user error (and may involve bugs). Always backup your save before editing.
Physical damage. The flash memory storing your save data physically exists inside your game card, and can be damaged through mistreatment. Store your cartridge somewhere it won't be exposed to the elements (e.g. water, extreme heat/cold), won't be damaged (e.g. dropped, handled by children/animals), won't collect dust, etc.
Interrupting the save process. If you turn the power off or remove the game card at a critical point while the game is saving, then the save will not finish properly and the game may consider it corrupt. If you follow the instructions, this is not likely to happen. There are several "glitches" that get involved with save interruption for the purpose of cloning Pokemon, etc. You run the risk every time you try something like that.
Data degradation. Flash memory degrades over time/ with many write cycles. Eventually, enough errors may accumulate that the game considers the save data to be corrupt or unreadable. This is very much a long-term proposition and you should not be scared of it, but it is worth listing here.
Bootleg/reproduction and second-hand games. If you have a bootleg or reproduction game, then the cartridge is not authentic and the ROM may be modified or the cartridge made improperly. If you want to be confident, always make sure you are buying authentic games (hint: they are expensive). If the game belonged to somebody else before you (or you cannot confirm that the seller sources the game legitimately), then you should be wary of problems with save data.
if the game chip gets messed up yes it can so take good care of it.
Not unless your game is severely glitched or hacked...games are designed so they don't do that.
If you don't mess it up you should be fine.
Not unless you do something to screw it up on a heck of a scale like absolutely ditching the DS at the floor with the game in. As long as it's a store bought copy, or you're able to trace it back, then it shouldn't randomly corrupt. If it ever does corrupt, you'd know what you did.
