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 Cavapoo, watch their breathing, their neck and how they cope alone. A Cavapoo who coughs at night, breathes faster while asleep or tires early on a walk may have a heart problem starting. One who scratches the air near their neck, yelps when picked up or hates having their collar touched may have neck pain from the Cavalier side. Young Cavapoos can find being left very hard, and that is treatable. Bloat (GDV, a twisted stomach) can happen in any dog, though it is most common in large, deep-chested breeds. A swollen, tight belly, retching with nothing coming up, sudden restlessness or drooling is an emergency: contact your vet now. None of these is bad behaviour, and none is something to wait out.
They'll keep sitting on your laptop. If their breathing changes while they sleep there, tell your vet.