Hey Sam,

It might be more helpful if you shared what you want to achieve. Something that I do to have a public facing IP that can redirect traffic from droplet to droplet is have a floating IP.

A floating IP is basically a static IP address you can use to redirect traffic to any of your droplets provided they are in the same data center. You can set one up by going to Networking - > Floating IPs tab - > then select the droplet you wish to assign the floating IP to. Just remember when reassigning a floating IP to a new droplet, the droplet has to be within the same data center as the previous one.

Hope that helps!

You can't.

There is no way to change Droplet IP.
Taking image and making Droplet from it is currently best way.

I wanted to add - maybe you can try contacting Support team. I'm not sure is they able to do it, but if they're, they'll be happy to assist you.