Board Thread:LotR Mod Technical Support/@comment-209.163.195.24-20181217055034/@comment-29620769-20181219061737

It's not really downgrading, your forge version is most likely either 1614 or 1558, and downgrading would mean changing that. And switching from 1.12.2 forge to 1.7.10 would be downgrading the minecraft version the forge runs.

But glad that it works now