How does one make up for unobserved Ramadan days over the past ten years, the number of which is unknown, and is feeding the poor obligatory along with that or not?

You have deliberately broken your fast in Ramadan, and you must offer sincere repentance and make up for the days you missed. If you are unsure about the number of days, only make up for what you are certain is obligatory. If you had no valid excuse for delaying the make-up fast, you are required to feed one poor person for each day you delayed making it up, and it is permissible to appoint someone to feed on your behalf.