If you install apps through crossover (and yes some that aren't listed as supported still work, it's trial and error there), you can uninstall them via crossover. If one that you want asks for internet explorer, then you can install internet explorer.
As for buying apps for linux, like you'd buy windows or Mac apps ? Well lots of them are freeware, yes there are commercial apps, but a number of them are "specialist" and can be bought from the actual vendor but online (I've certainly never seen crossover in the shops).
Rather than "trying to run before you can walk" Juvencio, I'd suggest that you run your system as dual boot i.e. windows and linux on the same machine, that way if you find that theres specific things that you have to do under windows (or until you find a suitable replacement to run under linux) then you have the option.
A slightly extended addition to that, is that if you made a partition that can be read by both windows and linux e.g. a FAT32 formatted partition, then you could easily do whatever it is that you want to do in the windows based app, then make a copy of any resultant file and store it in the FAT32 partition, and then see if you can do anything with it under the linux equivalent application.