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, and you'll need to sideload them again. As for sideloading, you need to download iTunes on your PC and install a sideloading application. I'd recommend Sideloadly.
You can download the .ipa files from the Telltale iOS Archive:
Season One
Want v1.4.0 instead -> Here.
Season Two
Mirrors: Mirror #1
Want original v1.6.0 instead -> Here.
Want original v1.0.0 instead -> Here.
(Huge thanks to ksagaming for providing a .ipa for MCSM S2 which fixes resolution issues)
You can find the episodes here:
Season 1 Episodes
Mirrors: Mirror #1
Season 2 Episodes
Mirrors: Mirror #1
Important: When sideloading the games: Click "Advanced Options" under the Apple ID option and make sure file sharing is turned on.