Generally:
A general POA would expire when the principal became incapacitated. If there is a durable POA that was executed when the principal was competent then someone must petition the court to be appointed the guardian. A court appointed guardianship would extinguish a durable POA.
No they will not be able to access funds. A power of attorney expires on the death of the grantor.
A will can't make you a power of attorney. There is no point in making someone a power of attorney if you don't tell them about it. And a power of attorney expires on the death of the grantor.
The power of attorney ends with the death of the grantor. Someone will open an estate in order to settle the debts.
They could be charged with fraud. A power of attorney expires on the death of the grantor.
There is no such thing as an irrevocable power of attorney. The principal (grantor) of the POA can revoke anything they have given someone else at any time they choose.
Nothing unless person is declared to be mentally incompetent at the time the power of attorney was made
In most (if not all) states, drafting a power of attorney for someone else is the practice of law. It must be drafted by an attorney, or by the staff of an attorney (paralegal or legal secretary) under the supervision of the attorney. POAs can also usually be drafted by the person signing it (but not by the person who is receiving the power of attorney), since in most instances it is authorized to practice law on your OWN behalf only. Many states have statutorily authorized forms that can be used by a grantor without an attorney, but if a paralegal independently (without attorney supervision) assists a grantor in filling out the form, this may be the unauthorized practice of law, subject to criminal or civil penalty.
The answer to your question will vary, depending on the extent of the power that you've been granted, and the capacity of your mother at the time she named you as an agent, as well as the language of the document itself. There are different types -- or "levels" -- granted by a "Power of Attorney" document.Because you've mentioned that your mother is "mentally challenged," it is possible that the POA you hold is no longer valid. If it was granted before she became mentally incompetent (IF she is mentally incompetent), and if the document doesn't declare your responsibilities "in the event of her mental incapacitation," the document is likely void.If your mother is mentally incapacitated, she cannot grant Power of Attorney to anyone, including you. Rather, someone needs to file a petition to be named as her legal guardian.Because there are so many variables, and because laws vary from state to state, you need to consult an attorney in your area. You should be able to meet with an attorney for an initial consultation without any charge to you.
The persons wishing to have the POA invalidated must follow the prescribed legal procedure according to the laws of the state in which the POA was granted. When a POA grantor dies the POA becomes invalid and the deceased's financial matters become the jurisdiction of the probate court and the executor of the estate. If no executor was named in the Will or no Will was current the probate court appoints someone to oversee the estate of the deceased.
A person who is incompetent cannot grant powers of attorney. Someone would need to petition the court to be appointed their guardian or conservator if that person needs assistance in handling their affairs. You should seek the advice of an attorney.
Someone who has no legal capacity, e.g. a person who is mentally incapable, a minor, etc.
Anyone can act as a power of attorney for someone else. You do not have to be an attorney