I have worked in a new website without using a localhost but a personal domain name.
I'm currently hiding the website from search engine by using the wordpress feature. I've also installed the plugin "Hide my Site" (https://wordpress.org/plugins/hide-my-site/).
When I'll finish the work, the domain name i have used so far will be replace by a new one. The domain has already been used so far and rank for some keywords.
If I start to work on the onsite SEO before changing the domain name, can it hurt the website?