If the patches are sequential (ordered) you usually have to install the previous patches first or it includes all of the patches. This is because it usually replaces the application as well as the files it relies on.
If the patches are non-sequential (such as windows updates where each patch fixes a different part of windows) then usually you need to download all of the different patches to have all the different fixes. This is because it only replaces the files that the program (windows) relies on. These files can be other smaller programs but since they're not related they can be upgraded separately.
Most applications use the 1st model for updates and so it's usually safe to say that if you have the latest patch you have all the fixes. I just wanted to make it clear that there are some exceptions to this rule (such as OSes)
If the patches are meant to treat the same thing, then I don't believe the application of a new patch will result in a recurrence of prior issues. It is more like taking drugs when you had already taken some that healed you. Talk to an expert for professional advice.