Time Machine question
Apple's support page for Time Machine indicates in multiple places that you can restore individual files as well as perform a full system restoration.  The site specifically states that Time Machine "...remembers how your system looked on any given day—so you can revisit your Mac as it appeared in the past."  Additionally, the support page also mentions being able to restore your entire machine by first booting to the recovery partition.  All of this would seem to indicate that, yes, you will be able to restore your machine to a specific date when your machine worked perfectly.

That said on older machines for which Time Machine was not available, I have had success using Carbon Copy Cloner to make an exact clone of my system drive at specific dates and times.  This would provide myself with a fully bootable backup drive that I could immediately swap into a machine for a minimum of downtime should I experience a drive failure.  This method, however, is more for the advanced user who has a Mac that is more easily serviced than many of the currently available Macs.