Are there any pre packaged fillings that you know must be refrigerated after being placed on cake?

also does german chocolate cake icing, need to be refrigerated?

How long can ganache be left out without being refrigerated, whether on cake or still in bowl?

I don't know of any sleeved filling that needs to be frig'd until it's been opened. Once on/in the cake is does not. For yrs I didn't know the opened pkg should be frig'd and didn't. No one ever got sick

Gr Cho is usually a cooked icing so it should not need refrigeration,.

Sorry don't know about ganache.....my guess is it is fine once on a cake for maybe 24 hrs? Leftovers probably should be well covered & stored in frig.