I think what you say is impossible
The DNS (Domain Name System) simply translates a domain name (e.g., chat.openai.com) into its corresponding IP address. That’s all it does: resolve a name into an IP.
So it’s impossible that changing DNS settings would “remove limits” or bypass usage restrictions. In the end, every request must still be sent to and handled by the servers of OpenAI, which enforce any limits on the server side based on the account — not on the DNS being used.
Additionally, using a different DNS provider (such as Cloudflare) does not hide or change your public IP address, nor does it alter your geographic location. DNS only handles name resolution; the IP address you present to the servers is still the one assigned by your internet provider.
So the “no limits” behavior is just a coincidence or a temporary effect — not a DNS-related hack.