Ubuntu – Reinstallation of Ubuntu WSL 18.04 and Python3-pip installation issues

I deleted and reinstalled Ubuntu by following the instructions here but the same issues with pip installation persisted even after I've reinstalled Ubuntu. I suspect that the re-installation process did not totally help me remove Ubuntu.

Just to be clear that the Ubuntu I am installing is a bash shell and not a disk image that requires partitioning – just downloading a copy of Ubuntu from Windows Store would do in my case

How can I cleanly remove all of Ubuntu bash files on (Windows 10 Version 10.0.17763 Build 17763)?

The steps I took to reinstall are:

1. Uninstall Ubuntu under programs and features
2. Deselect Windows Subsystem of Linux from apps & features
3. Restart on clean reboot (as prompted by windows)
4. Reinstall Ubuntu on Windows Store
5. Setup
6. Run sudo apt-get update
7. Run pip installation

I've seen other methods of uninstalling such as wslconfig.exe /u Ubuntu, but I did the aforementioned way because of the Fall Creators update which allows this method. I'm not sure what's the difference between them and if it will make a difference in my case.

However, the same pip issues persisted, does this way of reinstalling guarantee that I get a fresh copy of python environment? What have I possibly done wrong?

The reason why I wanted to reinstall Ubuntu is because my pip is not functioning properly on only Ubuntu and not on Windows OS. The example is as follows:
example

Any advise will be greatly appreciated. Thank you!

Further details about what other stuff I have tried to troubleshoot the pip installation

CACHING

Some recommended to use --no-cache-dir but it did not work and I even tried rm -rf ./cache/pip but that also did not work. So I reinstalled Ubuntu WSL, hoping that it will work but it didn't.

NETWORK ISSUE

ping pypi.org does not work and returns the following message and freezes
PING pypi.python.org(2a04:4e42:2::223 (2a04:4e42:2::223)) 56 data bytes

What I have done about this issue:

1.Tried disabling IPv6 as recommended by @Kulfy here

Got the following error:

sysctl: cannot stat /proc/sys/net/ipv6/conf/all/disable_ipv6: No such file or directory
sysctl: cannot stat /proc/sys/net/ipv6/conf/default/disable_ipv6: No such file or directory
sysctl: cannot stat /proc/sys/net/ipv6/conf/lo/disable_ipv6: No such file or directory

2.Copied and pasted the following into Ubuntu:
Tried with sudo and root with the command below

sudo/root

cat >/etc/modprobe.d/blacklist-ipv6.conf <<EOF
# Turn of IPv6 by blacklisting the module.
# Even though it isn't needed.
blacklist ipv6

EOF
$

It returned the following -bash: /etc/modprobe.d/blacklist-ipv6.conf: Permission denied

as recommended here but also did not work

3. Setting Preferences for IPv4 over IPv6

I have also set preferences for IPv4 by uncommenting these codes
and editing the file by doing

sudo vi /etc/gai.conf

and then… uncommenting

#For sites which prefer IPv4 connections change the last line to
precedence ::ffff:0:0/96 100
...
#    For sites which use site-local IPv4 addresses behind NAT there is
#    the problem that even if IPv4 addresses are preferred they do not
#    have the same scope and are therefore not sorted first.  To change
#    this use only these rules:
#
scopev4 ::ffff:169.254.0.0/112  2
scopev4 ::ffff:127.0.0.0/104    2
scopev4 ::ffff:0.0.0.0/96       14

This is as recommended
here

This still has not worked. So, it may not be an issue with IPv6