Unfortunately, there's no current (legal) way to disable the Adobe Flash killswitch, and I would obviously not recommend trying to illegally "crack" copyrighted games unless you want angry lawyers coming your way. (It would also require a great deal of programming experience.) The Flash shutdown really, really sucks for older Flash games, including some of my own favorites.
However, many clever and wonderful people have been working on archiving old Flash games, and some game companies have released non-Flash updates in order to preserve their games.
For Farmville 2...
It sounds like you've already discovered Farmville 2 Launcher +, which is Zynga's official solution to the impending Farmville 2 shutdown. This is the only official way to continue playing Farmville 2 after the Flash shutdown occurs.
The launcher states that these are the supported platforms - possibly your issue is that you're trying to run it on Internet Explorer or a non-supported version of Windows?
The FV2 Launcher+ is currently available only to users of Windows 7 and 10, on Chrome and Firefox browsers only. We are working on making it available to Mac users and on other browsers. It is available on Facebook & Zyngagames.com too!.
If you're having trouble installing the launcher, they also provide an installer walkthrough about how to download and open the file and install the game, including a video tutorial.
For other games...
There are tons of great projects that are archiving old Flash games so that they can work without Flash, in case you are interested in checking out other old Flash games. Some of the ones I've seen are Flash Game Archive and Internet Archive. The Flash Game Archive in particular now supports local offline play for many of its games.