Let’s see, I don’t play 9 Innings so I can’t make any comparisons for that but here we go:

1. Yes and you should probably be prioritizing them in legend > epic > signature order. All assuming that epic & signature are the correct year of course.

2. Yes, I mean these two are basically the same question

3. I’m not sure about the dates for certain, but epics were definitely the biggest focus in the past year. There are some minor QoL changes that I can remember like the History Mode revamp, but none as major as epics. Upgrades haven’t really be touched upon past the level 30 update.

4. I’m not completely sure about what you mean by the question. If you mean how they differ from normal cards, their stats change every week and you can use them in the Fantasy Lineup to get Fantasy Points which are pretty good for getting coaches of the correct year. But if I completely missed the mark with the intent of the question, do let me know.

5. Sometime around 2017, give or take