to be more spesific..
for the second option, when you press enter you can just roll your trail file, if you want to make changes to your part, assembly or drawing from your trail file you can do it by pressing e. With this way your trail stops running and therefore you can make changes or create a different model.
It is a flexible way for large assemblies, when for some reason, fails to regenerate (when you forget to make a backup), then play the trail file by pressing enter and press e to exit, just one step before the change that cause the regeneration to fail.
Practice with trail file, it is a very efficient option in Proe
regards
xcad