Will a sprained ankle ever heal 100%?

Usually heals. For residual pain after a sprained ankle an evaluation for a osteochondral talar dome fracture is needed. Mri or ankle arthroscopy may help.
Not all spaghetti. Is the same. Some ankle sprains are little nothings that need no treatment and heal in a day or two. Other ankle sprains are really torn ligaments which can leave the patient with a lifetime of problems. So, to answer your question, it all depends on the severity of the "sprain.".