Whats the best option - Settlement deed or Gift deed or Will

Hi All, I and my sister had done a release deed with consideration a few years releasing our ownership on Father's property after his demise to our mother (being legal heirs of my Father - Son, Daughter and Wife). Now my mother would like to transfer this property to my name (Son). I would like to know what is the best way to do this to avoid legal hassles later. 1. Based on my reading/understanding to avoid challenges in court later, it is best to do a Gift/Settlement deed rather than a WILL? 2. If you agree, which one should my mother do - Gift deed or Settlement deed? a. Is there any way to keep the life interest in Gift/Settlement deed? 3. Should we get my sisters agreement for gift /settlement deed again considering that she had already released it to my mother already? 4. I understand that Gift deed (without consideration) will not attract stampduty charges for transactions betweeen direct descendants (mother to son). Please confirm and what is the likely charge here? 5. I Understand that Gift deed will transfer rights immediately , but what should I do to do "name transfer" of property? Can I do it one shot? 6. I understand that gift deeds can be challenged based on the soundness of my mothers mind when she gifted it to me? Is there a way to mitigate this risk by getting a medical certificate or something and attaching it along with the Gift deed?