Your dog licks you for either of the two reasons:
It is their way of showing you love and affection. When they lick you, it also makes them feel good as it is their natural way of seeking comfort.
They are asking for attention. Dogs may also lick you if they want you to pet them or play with them.
Dogs stare at their owners to show affection, just like humans do. If you return the stare, your dog will actually feel loved. Mutual staring between you and your dog can also strengthen your bond and increase their trust in you.
When a dog lies on their back in front of you, they are in their submissive and vulnerable position. So, when a dog lets you rub their belly, it means that the dog trusts you and they feel safe around you. Rubbing their belly also releases serotonin for them and makes them feel happier.
Your dog will show the following signs if it loves you: