Framerate is used in Dwarf Fortress to measure the speed at which the game is running. To check your FPS (frames per second) in Dwarf Fortress, simply change [FPS:NO] to [FPS:YES] in init.txt, and your FPS will be displayed near the top right corner of the screen.
tzenes answer is strictly correct. There is however no way in the game to see a list of all dwarves with a specific labor enabled (ie: mining). You must iterate through all your dwarves to check.
However, a custom utility called Dwarf Therapist has been written to allow you to do exactly what you want to do.
The game intentionally does not allow you to quit without saving (or abandoning) and doesn't allow you to have more than one save per fort. The idea is that there is no going back. Losing is supposed to be fun.
However, you can get around this problem with a little trickery. Save the game. Then make a copy of your game folder. Then keep playing. If you want to load the previous save, just delete your current game folder and replace it with the old one. It's a lot of work, but it gets the job done.
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From the Dwarf Fortress wiki: