Seems unlikely to me that your buds are swelling given how cold it's been. Mine aren't swelling here in alternating heat and cold. Be that as it may the apple should be fine.

On the stone fruit you can cut off some small branches, bring them inside stuck in a jar of water, and see if they bloom. I haven't done this but I believe others have already reported damage.

I'm probably mis-using the term "swell". In late fall/early winter, I could barely notice any buds on the trees at all, and the ones that were there were tiny. Now the buds that are there are still very dormant, but I can see their silhouette from a distance. I'm not worried about them blooming this year; I'm just looking for signs of life from the trees.

Mine are doing the same. I was just out there looking at them in a foot of snow and they look 1/4 inch at least. I didn't notice them a month ago. However my rasps broke dormancy in my windowless garage and had multiple 6 inch white stems growing. I think I had them too far back from the door.