I opened *.ipa packages of versions RetroArch 1.6.7, 1.5.0, 1.3.6 to extract the compiled core from them(using 7-zip): result of all versions of “_interpreter”(from 2017) is the same(but this time the behavior has changed): doesn’t unload from the RAM, doesn’t load snapshots, games freezes(earlier versions without acceleration worked perfectly).
Now it became clear how theory this is possible to solve: using the basic code of from ReARMed 2013-2016, and the acceleration code from ReARMed 2017-2021.
I think that If application crashes on iOS9 and freezing on iOS5 are cause of same code, then there is a hope that the developers fix it in new versions. But if the reason is different code, then It is doubtful that someone will be engaged in this, since the iOS5 platform has long been not target, and it seems that a simple selection of the version cannot fix this bug.