How and how much time is linear lichen planus cured completely?

Skin/Tongue: Currently there is no cure for lichen planus but there are certain types of medicines used to reduce the effects of the inflammation. Lichen planus may go into a dormant state after treatment. Lichen planus can flare up years after used to treat lichen planus include: oral and topical steroids, oral retinoids, immunosuppressant medications hydroxychloroquine, tacrolimus and dapsone.

No cure: If it truly is lichen planus, i don't think there is a total cure. It can only be treated and managed, but never completely cured.