Because you are not at least 65 years old by the end of the year, you apply the 10% threshold to all of your itemized medical costs (which include costs related to your mother). If she claimed them on her own return, she could apply the 7.5% threshold.
Shifting income to a later year, such as where you defer taxable interest to the following year by purchasing a T-bill or savings certificate maturing after the end of the current year. Investments in qualified retirement plans provide tax deferral.