Family member convinces Alzheimer's person to sell one of her properties and now can't undo. Any advice?

A year after the fact is a bit late to reverse the sale. Even if you did, you would have to refund the full amount, plus interest. I'm going to guess that the money is long gone.

the they is the family lawyer who is just a general lawyer ( nephew ) who took a year to try to do anything even after being paid to file on this and then filed in wrong court so after refiling what is a elder lawyer

If his mother was never declared by a doctor as incompetent , then she can sign anything and it's considered legal. If daughter has POA, it does not mean that she controls grandmother's finances - if grandmother has not been declared incompetent and is no longer able to do her own finances. A person can be diagnosed with dementia but that doesn't automatically mean that they are incompetent. Dementia has different stages. If she was diagnosed and declared incompetent, then the sale is Null. If daughter's POA has been activated, then the sale is Null. I'd verify with granny's diagnosis medically and financially. Perhaps it's now time to see an elder law attorney to protect granny's assets/finances from her son.

The buyers - assuming they paid fair market value - fully expected the sale of the house to them to be valid. The property is theirs. If Sonny presented himself as being POA or signed his mothers name, then he broke the law. The probability is that he is going to do other things like this to his mother & his daughter.

If you want this to stop, you & your daughter either need to press charges on him, contact his probation officer or have a court order for him to stay away

Has grandmother been declared legally incompetent to handle her own financial affairs?

At the very least it sounds like Father has exploited his vulnerable mother. That is a criminal offense.

(Isn't drug addiction a sad tragedy?)

Who is the "they" who say nothing can be done?