Is it obligatory to make up for the fasting of the years in which one did not consistently fast after puberty? Do the sins committed prior to Hajj fall away with this obligation? Is expiation sufficient instead of making up [the fasts]?

You must make up the days you missed fasting and feed a poor person for each day, due to delaying the make-up until the next Ramadan (definition) began. If you do not know the number of days, you must investigate and be cautious to determine the number that absolves your responsibility. Hajj does not waive the make-up of missed acts of worship; rather, it is a debt owed that must be fulfilled. Hajj expiates sins, but it does not waive the obligatory duties for which one is accountable, though it does expiate the sin of delaying them.