5c does not need 10.3.4, and therefore there is no 10.3.4 for the 5c, the 5c has an updated GPS module that isn't affected by the issue.
10.3.4 is the same thing as 10.3.3, with the exception that 10.3.4 patches the GPS rollover bug.
The 5c will continue to work with or without 10.3.3 installed, it also works with earlier versions of iOS.
However i always recommend installing the latest update for your device, which would be 10.3.3, newer versions (like iOS 11, 12 or the current 13) were no longer supported by the aging hardware of the 5c, you can check which version you have installed if you go to Settings --> General -- > About.
Get help with iOS updates
https://support.apple.com/en-us/HT209571
Get help with over-the-air iOS updates
https://support.apple.com/en-us/HT201435
Get help with iOS update and restore errors
https://support.apple.com/en-us/HT204770