The iPod touch has actually had a better cpu than the iPhone 5C since 2015 :PI believe you can. I've seen people run the game on iPods. The only issue I can see is battery life. Hope that answers your question.
yes, now 5s is lower version , but i've searched this issue on the internet and i found in a forum that someone has installed this game on 5c then he reported there is a bug in the game but i dont know which version that isLooks like the 5S is the oldest phone the current version of the app supports. (The 5C is equivalent to the 5 in terms of specs). That said, sometimes older phones will let you install older versions of an app if there is one your phone supports. If not, then the game isn't available for that device. To check if your phone can run the game, just open the app store on your phone and see what it says when you pull up Stardew Valley.