Changes to the ACT?

I recently decided to study for the ACT instead of the SAT and took a practice test from 2015-16 (http://cdn2.hubspot.net/hubfs/360031/ACT-2015-16.pdf?t=1501363850318) (found the link on prep scholar). I got a 34C (35E, 35M, 34R, 31S) and I was pretty happy because it seemed I was better at the ACT than SAT, but then I found out there were changes made to the ACT in 2015 or something?? However, the ACT website has a free 2017/2018 practice test that’s exactly the same as the 2015-2016 one I took (https://www.act.org/content/dam/act/unsecured/documents/Preparing-for-the-ACT.pdf) so I’m confused as to whether it was a mistaken upload. I don’t quite understand the changes, did the questions/difficulty change? Will it affect my score? Could someone who’s had experience taking the ACT look at the practice test and tell me how it compares to the actual test? Thanks very much!