DNS Nameserver. Cannot access internet

A. Historical Background which might be causing the present problem.

I had upgraded to Ubuntu Desktop 18.04.06 LTS using Terminal
$ sudo do-release-upgrade -d
During the process I got the query
'Installing the upgrade can take several hours. Once the download has finished the process cannot be cancelled.
Continue [yN] Details [d]'

I got curious and pressed 'd'. I then did not know how come out and pressed (ctrl + C).
This left my laptop in somewhat of a midway state between version 16 and 18. Upgrade wanted to go to version 20

When I rebooted I problems such as (not in this particular order)
1. 'trying to upgrade ... unmet dependencies'
For this I used the forum link and ran
https://ubuntuforums.org/showthread.php?t=2416975
 and ran
$ sudo apt update
$ sudo apt full-upgrade
$ sudo apt -f install

2. Got infinite login loop. Fixed that.

3. Orange screen with no taskbar and no Beaver logo. Fixed that.

My laptop (Desktop 18.04.06 LTS) runs fine, except for the problem below
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B. Present problem

I cannot access the internet through Firefox

Here are some of the commands that I thought would be useful for you to diagnose the problem:-

margaret@Lappy:~$ systemd-resolve --status
Global
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test

Link 3 (wlan0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

Link 2 (eth0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
---------------------------------------------------------
margaret@Lappy:~$ sudo systemctl is-active systemd-resolved.service
active
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I tried doing this through Graphical User Interface (GUI). It shows it. When I change it in Terminal, with the below command, it changes in the GUI as well.
margaret@Lappy:~$ nmcli connection modify "WIFI 1" ipv4.dns "8.8.8.8,1.1.1.1"

--------------------------------------------------------
margaret@Lappy:~$ ping 8.8.8.8 -c2
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=120 time=27.7 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=120 time=25.7 ms

--- 8.8.8.8 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 25.700/26.737/27.774/1.037 ms
-------------------------------------------------------
margaret@Lappy:~$ ping google.com
ping: google.com: Name or service not known
-------------------------------------------------------
margaret@Lappy:~$ nslookup 8.8.8.8
** server can't find 8.8.8.8.in-addr.arpa: SERVFAIL
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margaret@Lappy:~$ nslookup 192.168.2.1
1.2.168.192.in-addr.arpa name = _gateway.