My mother is 65 years old. She had seizure for the 1st time. MRI report says Suggestive of neoplastic pathology and arachnoid cyst. Is surgery required? so is there possibility of Tumor? Or do we find that out after/during surgery?

Neoplastic pathology means any disease which causes a tumor, whereas arachnoid cyst means that it is just a fluid-filled sac and not a tumor, so the report merely suggests that there is a possibility of either 2 affecting your mother, but it doesn't conclude anything, so we can't be certain about whether it's a tumor or not.
For tumors, surgery will be the main line of treatment, followed by either chemotherapy, or radiation therapy, or both.
Arachnoid cyst wouldn't need a treatment, but if you do go ahead anyway, or if there's some complication that results from it, then surgery would be needed.
We are attaching our page which concerns neurologists who have a good track record and provide affordable services - Neurosurgeon in India.