Can we use coconut bits for that particular day thaligai to offer it for Perumal and then use the unused bits the next day or must we desiccate the whole coconut and use it as needed for offering?

If we break one coconut and use it for that day’s thaligai, we cannot use it again for the next day Tiruvaradhanam.
Notes:
We do not prepare thaligai for Perumal during the night; maybe we can use the remaining coconut for the food we prepare at night and offer the same to Perumal.