Yes, this tool is completely free to use.
Image URLs are a useful way to transfer images stored on your desktop to somewhere hosted on the internet.
Yes, you can use the image URLs generated from this tool to display images inside of emails by placing the URL inside of an <img> tag, like so:
<img src="your_url_here">
You can send emails with images directly from a spreadsheet with Lido, the spreadsheet that automates work for you.
Your URL will stay up as long as you're using it.