Quick home electric question

Well, yes and no
When I started this project I installed the breaker for the generator on the top right position of what I thought was the main box
The plan was to then buy an interlock switch which does not allow the main breaker and the generator breaker to be on at the same time, you would have to switch the main off before turning the generator on, and vice versa
But when I killed the 200 amp "main" breaker i found out it does nothing

Now, there is still the 100 amp breaker on the smaller panel, which does disconnect the house from the grid so, as long as I kill that one before I flip on the generator we are safe...but that is relying on me, with no real safeguards

I'll call the city tomorrow and see if there were any permits issued to the previous owners, that might shed some light on things
Yes, could be a dangerous situation there. A licenced electrician is your best bet. Regardless of cost.