Questions about Unlocked S8

[Mo4SHo]

I’ve been doing some research about flashing an unlocked S8 (US) to ATT so that I can have the HD Voice, video calling, volte, and wifi calling features. I just needed some clarification on some things.

I’ve read that if you just put in an active SIM card that you will not get those above mentioned features, but will I be able to make regular phone calls? I ask because I also read that if the IMEI is not recognized by ATT (which I found to be true since the unlocked version is unbranded) that only the WiFi feature will work.

My other question follows up on after flashing the phone. After I flash the phone with ATT’s firmware, how will the above mentioned features work if the IMEI is not recognized by ATT? Will the flash change the phones IMEI or will I have to do one of those IMEI generators to get a working IMEI that will be recognized by ATT?

After flashing to ATT, will I get all the bloatware? And since the updates/security updates schedule varies between branded and non branded devices, will my ATT flashed S8 be on schedule with ATT updates or not?

I’m hoping this will be my first android device if I can get these questions clarified.

Thanks!