Repeat the nth last command in vim

Building on the :s/pattern/replacement/gc idea from Samus_ (which seems to be the simplest way to ensure correct operation when pattern is contained within the replacement string), to replace the 2nd through 4th occurrences on a single line:

:call feedkeys("nyyyq") | s/pat/string/gc

feedkeys() is a function that stuffs the input string into the keyboard input queue. The point is to do the counting upfront so you don't have to worry about losing count or getting interrupted.

For a more general case, to replace the Mth through Nth occurrences on a single line for N greater than or equal to a very large M:

:call feedkeys(repeat("n", M-1) . repeat("y", N-M+1) . "q") | s/pat/string/gc

Replace M and N with the values you want (you can even let vim do the trivial mental arithmetic if you don't want to do it yourself). Note that . is VimL's string concatenation operator. Obviously this only saves keystrokes for large M. If you use this functionality frequently, it may save you time to put the above in a custom command or function of some sort, as it is quite a bit to type.

You don't need to suspend Vim history. The actual data forms a tree, and you can retrieve it with the undotree() function. There are, of course, a number of plugins that turn that into something more user-friendly, f.i. gundo, mundo, and undotree. If you also enable undo persistence (cf. :h undo-persistence) you can easily navigate through the entire change history of a file.