anyway to get the domain name from the ip ??

[DeaD_EyE]

>>> print(socket.gethostbyaddr('63.245.208.212'))
('redirects.public.mdc1.mozilla.com', ['cleopatra.io'], ['63.245.208.212'])
>>>

I guess you changed the ptr. Changing NS-Records takes time until they are everywhere (nameserver/resolver) updated.
To check the answer, you could do following on Linux:

andre@DESKTOP-F29NT09:~$ dig @1.1.1.1 63.245.208.212.in-addr.arpa ptr

; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> @1.1.1.1 63.245.208.212.in-addr.arpa ptr
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15931
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;63.245.208.212.in-addr.arpa.   IN      PTR

;; ANSWER SECTION:
63.245.208.212.in-addr.arpa. 86400 IN   PTR     coquide-cambrai-gw.gw1.lil1.fr.uu.net.

;; Query time: 35 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Fri Aug 09 12:57:47 CEST 2019
;; MSG SIZE  rcvd: 107

In this case the amazon-nameserver is used to query the PTR record.
The format is ip-address.in-addr.arpa
This will resolve the PTR record in a domain-name.