Some of this is not a training problem, and treating it like one wastes time your dog may not have. If they are distressed when you leave, if they growl or guard their food, their toys or you, if they are frightened on the lead, or if anything about them changes suddenly at any age, contact your vet the same day. A tip from a website, ours included, is not the answer. If it cannot wait, contact your nearest emergency vet now.
With a Papillon, watch their energy and their back legs. A young dog who goes weak, wobbly or very sleepy may have low blood sugar: contact your vet now. Bloat (GDV, a twisted stomach) needs the same speed: a swollen, tight belly, retching with nothing coming up, sudden restlessness or drooling. It can happen in any dog, though it is most common in large, deep-chested breeds. A skip in their step or a held-up back leg can be their kneecap. In an older Papillon, a cough or faster breathing while they sleep can be their heart, and pacing at night can be Cognitive Dysfunction Syndrome (dementia in older pets).
They'll never sit still for your phone. If they stop jumping, contact your vet the same day about their knees.