Power of Attorney

How do you change your power of attorney?
if I give a person power of attorney and I decide to designate someone else later must my lawyer notify the first person that they no longer have power of attorny?
Do you need a durable power of attorney for a joint bank account?
My father-in law's mental state is beginning to deteriorate due to dementia, why would my mother-in law need durable power of attorney if their bank accounts are joint? She already has a patient advocate for health.
Can a lawyer add a name as a Power of Attorney without asking?
The lawyer who drew up a Power of Attorney for my mother inserted his wife's name as the back-up, in case neither my brother nor I could function. Is this a recognized practice? If so, shouldn't he have asked first? If not, what should we do?
What type of Power of Attorney is needed for the bank to allow me to sign for my mother?
My mother wants to give me power of attorney to me to be able to choose a mortgage and sign contracts for a loan on the house we live in. The bank will not accept my Durable Power of Attorney for my mother.
What do I need to grant my parents emergency decision making for my children while I'm out of the country?
My husband and I will be vacationing out of the country. While we are gone, my parents will be watching the kids. Is there anything that I should sign giving them temporary custody or right to make emergency medical decisions while I am gone?