If someone has a belief, rejects it, and then returns to it, the person might say, "I've gone full circle."Its this sentence grammatically correct
No.
and what does it mean?
The expression "full circle" means "all the way around and back again." It's always used figuratively.
“I am full circle.”
I heard it said on TV “In the last year, I am full circle.” as the character has gone through so many changes.
Okay, I see.I heard it said on TV “In the last year, I am full circle.” as the character has gone through so many changes.
In BrE, it's almost always "I have come full circle".