Regarding gratuity and relieving letter

Dear Sir, I had worked with a firm for 10 years 6 months and 21 days.( from the date of joining till the date of resignation) Unfortunately in this tenure last 6 months due to my mother health I couldn't attend the office on regular basis as she was hospitalised.The last salary which I withdrawn for 26 working days after that I was working from hospital. But later was not given any salary despite I was sending official mails and making calls.( internal and external official mails) for complete one month. Later I send a mail stating the condition of my mother and requested for LWP and attached the medical certificate stating that I being the only sibling taking care of my mother so couldn't attend the office for a month or so.but Inspite of replying to that mail they disconnected my offical mail id and the offical sim connection without my knowledge. But by the end of the month my mother died and I even went through health issue and couldn't sent any mail further. Later after 1.5 month I written my resignation stating that I didn't attend office due to my mother demise and my health condition.( Exactly 90 approx days I didn't work at all). I got the acceptance from them within a week or so on the same mail. Now my question is related to my gratuity and relieving letter. 1. Now they are deducting the money from the gratuity for not serving the notice period.( despite they never given me salary for the month in which I worked from home for 1 month for which I have official mails). Can they deduct this amount.? 2. They are giving me a expereince letter till the time I attended my office.( means 04 months prior to my resignation). Is it correct? These all things are done verbally and have not given me anything in written.( leaving resignation). If No, please provide the legal right and procedure to follow Awaiting for an early reply. Thanking you inadvance Vik