Query Regarding Ischemic Stroke.

I am asking this question for knowledge purpose only. My father had 2 ischemic strokes in last 2 years  in PCA territory and Lacunar Territory. He takes medication like Aspirin 150 MG, Atrovastin 20 MG , Citicoline 500 MG and Piracetam 800 MG according to Doctor's advice. I have question regarding Antiplatelate drug Aspirin only. Can you please clarify that if Aspirin helps to dissolve the blood clot in artery which already happened ?  Or once the blood clots there is no way to dissolve it ? Only Aspirin will help to prevent blood clotting in future ? One more follow up question. Once there is clot , it is natural that adjacent tissue will die due to lack of oxygen and nutrient. Are those tissues salvagable with time ? Or generally tissue will not repair ? Only other part of the brain will take over and form new neural network to recover the functionality got affected by ischemic stroke. Please give a logical answer with medical terms. I have some background to understamd that answer!