Clarification on flashing original firmware

I have a galaxy s6 bought from malaysia and it was region locked. I initially thought it will be easy to unlock but I couldnt unlock it so I took it to local mobile service center. There they unlocked the phone. I dont know how they unlocked it but I think he used some box like octoplus. When I recieved the phone from him it was rooted and the knox counter was tripped.

I know I have voided the warranty but thats fine. Now I dont recieve any updates from Samsung. I want to flash the original samsung firmware back and I have the following clarification before doing it by myself.

1. If I flash the original samsung firmware using smart switch or odin will the phone be unrooted and will I start receiving updates
2. Currently in my smart manager-> device security it says security threat found and I get the notification "unauthorized action detected restart your device to undo any unauthorized changes". Will this error message go off and will the device threat go off.
3. Will installing My knox cause any problem or I should avoid installing it ?
4. Currently "In find my mobile" remote controls is not getting enabled. Will the find my mobile feature start working after flashing the official firmware.

Thanks in advance
Rahul