Can we enable camera 2 api without rooting the device?

short answer- no.
BIG ANSWER - STILL NO
And if your planing on rooting a samsung then I would say keep some money for the new one you going to need after you dash this one.

No!
And Never Root Your Device Expect If It's Very old And Use it As Secondary Device Because Rooting Causes Many Security Problem Like Knox,Secure Folder 📂 Don't Support etc.The Device Will Get Bugs As Well As Lags.

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No you can't.