ACT Prep Guide 4th Edition

I currently have the 3rd Ed (“The Real ACT Prep Guide”) and heard that it’s very outdated. Would it be bad to use the practice tests in the 3rd edition or would I be prepping with the wrong materials?

Can anyone explain what the changes they’ve made to the test are (aside from the essay) that’ll surprise me (since I’ll be prepping with the 3rd Edition) when I take the actual ACT?

From what I understand unlike the SAT the ACT hasn’t changed in years so I don’t think it would be much of a problem