If a user deletes all data from QuickBooks than does that data gets deleted from all platforms

Hello there, @nidhi-das.

I've got some insights to share on what will happen if data will be deleted in QuickBooks Online.

If a user deleted all your data in QuickBooks Online by purging the company file, these information will be completely eliminated in the system. That said, we can no longer locate any reference of the transactions.

However, if the user was removing the data (customer's and vendor's entries) manually in the system, yes, this will be deleted in all platforms or all users end. 

Thus, you can still visit the Audit Log section on your account. This area keeps track of your activities, where you can see who made changes to your books and what they did. It's also a good place to check on those transactions that were banished.

For your reference, I'm also adding here a link that you can scan through about voiding and deleting entries in QuickBooks Online, in case you need them in the future: Learn how to void or delete invoices, expenses, and other transactions.

I'm always here to lend a helping hand if there's anything else that you need, @nidhi-das. Have a nice day!