Hey, I was testing mobile miner a while ago on my Samsung android tablet, so you can check my results below in quote. I don't think it will be much profitable to run it on old ARM, but if you run it 24/7 you will get few coins for sure.
I have just installed and tested the app on my Samsung Galaxy Tab S2. It's a SM-T719 octa-core model (Qualcomm MSM8976 Snapdragon 652) and on 8 threads with 90% CPU usage it showed 26-28 H/s. About iOS version, Apple recently banned all crypto mining apps from their app store, so we probably won't see Webchain Miner on iPhone.