If the outer pot has no drainage hole, and the inner pot does not reach the bottom, it's possible the outer pot has a lot of water in the bottom which may, or may not, be in contact with the plant. Sitting with its roots in water for a long period can kill a plant, but by the look of your plant, it looks more dessicated, that is, it's suffered significant drought, so the other possiblity is that, because the inner pot does not go to the bottom of the outer pot, any water you put into the plant simply runs straight through and is sitting inside the outer pot. This can easily happen if the plant has been allowed to dry out too much - when the soil in the pot is dry throughout, water will just run straight through.
You need to lift the plant out of the outer pot to see what has happened, but either way, if you want to try and save your plant, it's probably best to cut it down to about 2 inches, stand it in something else that's big enough for it to sit in properly, like a tray, water well and keep watered aas necessary ongoing if it shows signs of growth. Do not apply any feed, fertilizer or vitamins, just use water - the plant is unable to take up any fertilizer anyway, in its current condition.
In terms of ID for the plant, it's difficult to be certain because it's nearly dead, but it could be Leucothoe axillaris 'Curly Red' - it has pinkish red new growth in spring, which then turns plain green. It also produces small white flowers in spring. If it is/was that, Leucothoe does not like to dry out; it prefers damp but well drained soil conditions, and prefers partial shade. It is not a plant that recovers well from drought. See here https://www.gardeningexpress.co.uk/leucothoe-axillaris-curly-red-unique-twisted-evergreen-foliage for images and some information on the plant.