I didn't seem any apps like boinc or fah on app store, is it possible to run it on iOS devices?

P.S. Also wanna know is there an app can do this on even older android devices?

Yes, I've ran boinc on Android 4.4.1 and 4.0.1
It's not very efficient, because the devices would often overheat, and are very slow.
I'd actually say that the first Android devices to run boinc, that make sense, are the newest gen 8 to 9 nm 6 core designs.
They still keep the battery below 35C when crunching data.
On some dual core 1,2Ghz Android 4 devices, I could only run 1 core.
That's not only 6x slower than a modern one, it also runs at 1,2Ghz, vs 1,7-2,5Ghz on newer devices (another 30-50% slowdown), as well as the architecture itself being slower (slower RAM, emmc, etc...).
So you'd be wasting 3-5 watts of energy, to run a job well over 10x slower than on a modern phone.

I didn't seem any apps like boinc or fah on app store, is it possible to run it on iOS devices?

P.S. Also wanna know is there an app can do this on even older android devices?

From what I understand, you will never see any BOINC or FAH apps on the MacOS appstore because they require all Mac apps to be signed.

So you will have to install BOINC from the website and any MacOS compatible apps from project websites. Not many projects support Apple OS'. But some even support the latest ARM based Macs like Einstein.
https://boinc.berkeley.edu/download_all.php