There is no way to get the iOS version legitimately.
First, you need to check if your iPhone can be jailbroken. There is a comprehensive list of jailbreaks with their corresponding jailbreaks here. If your iOS version is not jailbreakable, you need to stop updating and wait for a jailbreak to become available (if it ever does.)
If you cannot jailbreak, you can still sideload MCSM Seasons One and Two, but they will only stay for 1 week. Every seven days, you will need to reinstall them. This is a limitation by Apple to prevent As for sideloading, you need to download iTunes on your PC and install a sideloading application. I'd recommend Sideloadly.
Important: When sideloading the games: Click "Advanced Options" under the Apple ID option and make sure file sharing is turned on. This is required for the app the read the episode files.
Megathread v4.2 | New 64bit Android builds and MCSM web port, out NOW!
★ IPA Downloads ★
Episode files
Extra/Alternative files
Jailbroken Process
With each jailbreak, there should be some sort of .ipa installer (you'd commonly find Trollstore as one on iOS 14-17.0), and through that you can install the entirety of S1 and S2.
Use a file manager like Filza or iFunBox and go to this directory: /private/var/mobile/Containers/Data/Application/Minecraft and replace the "Documents" folder with the episodes file found in the link above.
We'd recommend clicking the share icon, then selecting "Filza" before copying it to the above directory.
Non-Jailbroken Process
If you aren't jailbroken, and you have installed it with filesharing enabled, a similar directory should be available from the "My iPhone" section on the files app. The folder there should be the same as the documents folder. Delete the contents of the folder. Next, get the contents of the documents folder with all the episodes and paste them into the one you just emptied with the MCSM icon on the folder.
Note: There are many S1 .ipa files floating around online. The one to get is the 1.7 version, unless you're on a 32-bit iOS version, then install version 1.4. 64-bit devices also support version 1.4. Some even prefer version 1.4 over 1.7 because the 1.4 episode select UI is more faithful to the PC and console ports (only on mobile, on iPad there is no difference), however the resolution for v1.4 is lower for iPhone 6 and up. Both versions are found in the link above.