PokerTracker

I can only do so the day of a session before I close PT4. Once it's closed, I haven't been able tore view a session from say... Yesterday, or last month, etc.

You can filter to marked hands anywhere in View Stats when you're seeing individual hands, just use the View Marked Hands Only checkbox. Another way that might work well for you is to create a Hand report in My Reports and set it to display hands of specific tags. You can save the report and then bring up the hands with those tags quickly and easily.

Thank you sir, much appreciated!

For some reason my hands are all being auto-tagged to a custom tag I made. How can I fix this?

There is no automatic tagging in PT4. Are you using some form of hotkey software?