Can we remotely activate and see current heart rate of a person in his apple watch using his paired iphone?

No, neither remote activation nor on-phone monitoring can be done.

Live Heart rate can only be seen on the users own Watch.

Kind of… How to mirror Apple Watch screen on iPhone.

https://youtu.be/SohJsgVzc4Y

Hope this helps.

Oh that's a cool truck

But not on Watch SE, nor on Series 5 or older AFAIK