My question is: I recently got back into playing and I haven't played many tournaments. I was told that if I have a card that has been reprinted in legal expansions, for example Diabolic Tutor or Shock, I can play even the older version from 7th ed. or Odyssey. Is this true? Thanks
Yep/ Any printing of a card is legal in a format as long as that card has been printed in a set that is legal in that format. So, your Shock from Stronghold and Tutor from Odyssey are both legal in the current Standard.
Thank you so much. Also one other question on the same line. Since the Counterspell is also a reprint, even in the masterpiece form, does that also mean I can use 7th ed or masks version? Again, thanks
No. You can use the 7th edition version in any set where the Masterpiece version is legal. However, the Masterpieces are not Standard (or Modern) legal just because they are printed along with the Amonkhet set. They are considered outside the set and are "extras". Their printing does not change the legality the cards had before their printing so in this regard they are different than normal Standard reprints.
So I hate to seem mental or redundant, but that means I can use Counterspells from say, 7th?
Not in Standard or Modern as Counterspell has never been printed in a Standard Legal set after 8th Edition. The Masterpieces are not Standard Legal so they do not change anything with existing legalities. It would have had to have been printed in Amonkhet proper to have changed the legality. Since it wasn't, it is not Standard legal.
You can use 7th edition counterspells in any format where counterspell is already legal.
You can use 7th edition counterspells in any format where counterspell is already legal.
For Counterspell, it is only legal in: