If I have a portfolio website connected to my domain name and hosting, and I delete it from the hosting, will it still be on portfolio so I can simply reconnect?

Adobe Portfolio is hosted on Adobe’s servers.  No 3rd party hosting required.

From whom did you purchase your custom domain name? 

1. Was it part of your hosting package?

2. Or was it was purchased separately through a domain name seller’s site like Network Solutions, GoDaddy or Namecheap.com? 

If the former, contact your hosting provider to find out if you can use the same domain name with Adobe Portfolio.

If the latter, you can edit your domain’s DNS settings from the seller’s portal to point to your Adobe Portfolio site. For more details on that, see link below. 

https://help.myportfolio.com/hc/articles/209448927-Connect-a-custom-domain-to-your-Adobe-Portfolio-Site

Hope that helps.

domain name changes you make with your registrar won’t affect your adobe portfolio. 

hosting is another matter entiredly and makes no sense because adobe’s portfolio is hosted by adobe and can’t be changed.