Simply download the title with UA Connect to begin using the native version.
Yes! If you own or purchase a UAD-2 plug-in that has been ported to UADx then you can get the UADx version for free.
I already own the UAD-2 versions of some of the plug-ins available in with UAD Spark. Since UADx plug-ins run natively on your computer’s CPU, you may run as many UADx plug-in instances as CPU can handle. How many UADx plug-in instances can I run in my project?