I have been a loyal iPhone user for years. I did have two Apple IDs previously. The other one has already been deleted by Apple formally.
The current Apple ID I am using was set up years ago when you had the option of opting out from iCloud features. So basically the iCloud was never set up at the first place with regard to this ID. Under my ID profile in the setting, the iCloud status was off.

So can I confirm if my data of phone were all kept locally on my device without being uploading to any cloud own by Apple without my knowledge?
I am not using Safari for either but Firefox or Google Chrome. Even if you have an iCloud activated, would the data of these 3rd party apps also be transmitted to Apple Servers through iCloud?