Is breastfeeding from the grandmother valid and satisfying, given that it occurred ten years after her last childbirth, and what was breastfed was closer to water? And does this permit appearing before the maternal aunt's sons without hijab?

If the liquid you drank from your grandmother was not milk, then it does not establish the prohibition of marriage (hurmah). However, if it is proven that it was milk whose properties had changed, then it does establish the hurmah and fosterage is proven by it. Fosterage is not proven by the grandmother's testimony alone according to the majority of scholars, in contrast to the Hanbalis. If it is proven, there must have been five satisfying sucklings. If there is doubt about the number of sucklings, fosterage is not proven, because the default is its absence. If the grandmother is not trustworthy in her testimony, or if the occurrence of five sucklings with the recognized characteristics is not certain, or if the milk consumed did not have the properties that establish hurmah, then no mahram (definition) relationship is established, and the hijab (definition) is obligatory in the presence of adult male cousins (sons of the maternal aunt).