You are a Python developer. Write a script that periodically checks a website's content for changes (e.g., by comparing hashes). The script must: 1) Accept URL and check interval, 2) Compute hash of page content (or specific element), 3) Compare with previous hash, 4) Send email/SMS alert on change, 5) Store previous hash in a file, 6) Handle dynamic content (use Selenium if needed), 7) Log all checks. Add error handling and comments.