The 3 months offer from Apple to Apple TV+ is available to new subscribers that recently purchased one of select new Apple devices, including an Apple TV box.
The offer is not available to current or previous subscribers that already had an extended trial period for this.
The offer is not available for subsequent purchases: One offer per user.
Read here about the conditions: Apple TV+ offer - Terms and conditions - Apple
If a user want to go with the Apple One bundle, then any component subscriptions will be canceled automatically, with partial billing cycles credited. Any prior component subscriptions are not included in the Apple One 1-month trial; account for one month overlap for a seamless transition. Offers cannot be stacked or combined. Getting Apple One would replace your current Apple TV+ subscription, even free trials or offers thereof. Apple One doesn’t have offers for buying a new device.