As the database changes? New iblock or the properties desired for a new design? Component settings? If not, then just as Nicholas had suggested, create a new template, preferably a separate user group, this group put a condition to display a new template, and right on the line of the work site.
If the changes are not just the layout, it is still better to create a copy of the site. In the case of Bitrix Env login root access on the server, from the menu choose manage sites in the pool and create a new site with its own kernel (kernel). Copy via a backup, if server space allows. If the name of the website when you create a to write .<your domain> and in the settings there is a DNS A-record *.domain.ru create a website automatically will work on the subdomain.
Mabel answered on July 2nd 19 at 18:09
Just make a separate folder and point it to the new template