Is it considered a Bid‘ah (innovation in religion) to single out Mondays to Thursdays, Saturdays, and Sundays for fasting, while refraining from fasting on Fridays unless it coincides with the Ayyam al-Beed (the 13th, 14th, and 15th of the lunar month)? And what is incumbent upon someone who has negligently missed obligatory prayers and the Witr prayer after Ishā’ and does not know their number?

If you fast on the two Eid days, you have fallen into innovation (bid'ah), for fasting on them is forbidden according to the Prophet's (peace and blessings of Allah be upon him) saying: "These are two days on which the Messenger of Allah (peace and blessings of Allah be upon him) forbade fasting: the day of your breaking fast after your fasting (Eid al-Fitr), and the other day on which you eat from your sacrifices (Eid al-Adha)." Similarly, fasting on the days of Tashreeq is forbidden according to the majority of scholars, except for the pilgrim performing Tamattu' who could not find a sacrificial animal (hady). As for continuously fasting throughout the year, while breaking fast on the forbidden days, there is no harm in it as long as it does not weaken you. The prayers you missed due to laziness must be made up, and making them up is not waived due to not knowing their exact number.