Paste a web address and get a QR code that opens it when scanned with any phone camera. Shorten long links first so the code stays simple and scans reliably, then style it with your colours, a frame and a centre logo.
No. The code simply contains your link, so it works for as long as the web page is online.
Shorter links produce a less dense code that scans faster and from further away, especially when printed small.
Not for a code that contains the link directly. If you may change the destination later, point the code at a page you control and update that page.