Use this app on another device
There are no accounts: you are this browser. To be the same person on your phone and your laptop, link them. Then either can delete what you've posted from both.
On the device you already use
On the new device
Type the code here. This browser then becomes that person: anything it posted before stays up, but can no longer be deleted from here.
Only show a code to yourself: whoever types it in becomes you.