How to write a rule to prevent any deletion of node from database

Question

I am trying to write rules to secure database. But I am confused on writing a rule which will prevent from deleting any node from database. I have read regarding newData.e

Answer 1

To allow adding new nodes, but prevent deleting or overwriting any node:

".write": "!data.exists()"

To allow adding and overwriting, but not deleting, any node:

".write": "newData.exists()"

Update: screenshot of the simulator for these rules