How do you know you didn't already reach stream entry a few lifetimes ago

Buddha says, you only have 7 more lifetimes after hitting Stream Entry. Wouldn’t it make sense that current Buddhist monks reached that stage a few lifetimes ago? How would you know if you already reached Stream Entry last lifetime?

And what would it look like if a child was already born without the lower three fetters? :thinking:

What would it look like if a once-returner was reborn without the lower three fetters and with the next two fetters substantially weakened?