I don't understand why you would still want to membership admist rejection. What ever be your unavoidable reason here is a tip for you. It works.

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I was removed from a group three days ago, I got vexed and promised the admin that I will find a way back into the group and cause trouble.
That same day, my whatsapp started giving me problem, my messages won't send on time but I receive messages on-time, so I decided to wipe my whatsapp. Luckily for me (you will soon know why I said luckily), I forgot to backup my whatsapp data.
After I wiped my whatsapp, I went to reopen my account, then it asked me to restore back, but the date on the backup was October 3rd, so I just decided to restore it. When it was done restoring, to my surprise, I saw the group that I was kicked out on my account, I was so happy that I caused trouble in the group again, the admin was very surprised. Now you know why I said luckily ... You are laughing right.
let's go straight to business

How to recover your lost whatsapp group

uninstall your whatsapp(scroll down to see how to wipe your whatsapp)
Install your whatsapp again
Add your account then restore your backup to the date you were still in that group

How to prevent being kicked out of a group

Go to setting on your whatsapp

Go to chats
Click on backup chats

Click on backup to google drive

Then tick "only when I click on backup"

Now create a backup.

When you are being removed from a whatsapp group, just wipe/uninstall your whatsapp then restore backup.

How to wipe your whatsapp data

Go to your phone's settings

Click on storage and USB

Click on phone storage

Click on apps
Then click on whatsapp

Click on clear data

ref

How to rejoin a whatsapp group despite removal. (Needless of admin right)

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