Is it possible to specify dns records from different hostings on one site?

Question

Domain Name System

Good afternoon, there is a site that has been spinning for many years and then the customer decided to make a new site, I did it, but when the question arose that it was necessary to disable the old site and upload a new one there, the customer said that he did not know any data, everything was lost, he called everyone who can and eventually got hold of a login and a pass from reg.ru. But when I went there, the domain name was not there, but there were dns records where there was a redirect to a remote server. I had to change this address to my server where the new site lay. But what actually happens? A couple of hours have passed and someone opens a new site, and someone has an old one. And I log in from the phone, a new site has opened, then I turn off the Internet and turn it on again and, miraculously, the old site comes out. I have a question, could the person who made the old site, for example, go to nic. ru and there also make a dns zone with a redirect to a physical server, and then go to the masterhost and do it there too? As a result, some of the entries lead to the new site, and some to the old one, or do I panic early and just have to wait? Thank you.

Answer 1

DNS records have not been updated everywhere yet.
Depends on the provider.
You need to wait up to 48 hours for everything to be updated.

Answer 2

NS records are updated incrementally. Wait three hours. First, it is updated in the root zone, then it is gradually read from there by various providers. But among the NS records there is a main, primary master. It is one and points to one DNS server. Therefore, there is only one working DNS zone with the rest of the records.