What is meant by "sequence" in making up missed prayers, and is it obligatory to make up the missed prayers of a single day according to one's ability, or is it permissible to divide them over several days?

Missed prayers (fawa'it) must be made up in the order in which they were missed. As for how to make them up, you should perform as many prayers as you are able, at any time of day or night, in addition to the five current obligatory prayers. You should continue doing this until you have made up all the prayers you owe. If you do not know the exact number of missed prayers, you should make up what you believe is sufficient to clear your conscience. If the missed prayers are numerous, you must dedicate yourself to making them up, as long as it does not cause you undue hardship in your body or finances. If you do not know the exact amount you owe, you should repeat prayers until you are certain your obligation is fulfilled. If you forgot a specific prayer from a day but do not know which one, you should repeat the prayers of a full day and night.