My question is
1. Does the release deed is enough to keep the property with A and B?
If the property devolved on your mother then she can transfer the proeprty by a settlement or gift or sale deed to anyone's name i.e., to A and B also.
Since neither A nor B, C or D have any rights in the property during the lifetime of your mother, there is no question of relinquishing her rights and it is not the proper procedure in this situation.
If Chandan is reported to have died, what about the legal heirs of Chandan, by the way how is Chandan related to Rupa (your mother), this clarification would get you more proepr opinion.
2. Can I also get power of attorney from my mother?
You can very well get registered power of attorney deed from your mother if she is willing, but that will not entitle the title to property to your name.
3. Does it look suspicious that I got release deed and my brother got power of attorney and again I get one more power of attorney? How does it look in the eyes of judge.
This clearly appears to be an act fraud to cheat one particular person, instead your mother can apply straight jacket formula, i.e., to cancel the registered release deed and transfer the proeprty to A and B by a registered settlement deed which will solve the entire problem because nobody can question her authority of doing so.
4. What should my next move as my mother may go to my brother’s anytime as she is not completely aware of truth.
You can advise your mother of the step suggested above for an amicable settlement
I am aware that same general power of attorney can’t be given to 2 of her sons.
You are right in your understanding