```python
from typing import *
from collections import deque

def trace_relay(links: dict, start: str) -> list:
    if not isinstance(links, dict):
        raise ValueError("Links must be a dictionary.")
    
    if start not in links:
        raise ValueError(f"Start post '{start}' is not found in links.")
    
    visited = set()
    watch_path = deque([start])
    
    while watch_path:
        current_post = watch_path.popleft()
        
        if current_post == '':
            break
        
        if current_post in visited:
            raise ValueError("Handoffs cannot form a cycle, visit already occurred.")
        
        visited.add(current_post)
        
        next_post = links.get(current_post)
        if not isinstance(next_post, str):
            raise ValueError(f"Next post name '{next_post}' is not a string.")
        
        watch_path.append(next_post)
    
    return list(watch_path)
```