Reviving a Samsung Galaxy III Mini (GT-I8190N)

I have an old Samsung Galaxy III Mini (GT-I8190N) that was running O2 (UK telco) firmware and the latest Jellybean browsers: Chrome 42, Firefox 68 etc., that worked with TLS 1.2. I've flashed the firmware with the last Samsung BTU 4.1.2 Jellybean firmware, which takes Chrome down to version 28. That doesn't work with TLS 1.2, and attempting to update via Google Play fails with "Error: No connection", which I'm assuming is also a TLS error. What steps do I need to take to restore Google Play so I can patch the apps to the same versions as the O2 firmware? Edit: Post Robert's answer: I sideloaded a 24.x version of Google Play Store and a 20.x Google Play Services. That got things moving again. They updated to 25.2 and 21.33 respectively. A sideloaded earlier version of Firefox wouldn't update, but the APK of 68.11 is available from Mozilla's servers. Chrome, Firefox, Opera and Opera Mini all work with TLS1.2. The stock Android Browser 4.0 doesn't.