These days are the best days of the year as we were told by our Prophet salla Allahu alaihi wa sallam.

One can do all good deeds such as fasting, praying and charity.

The reward mentioned in the question is not authentic.

What is convenient to do during the 10 first days of Dhoul hijjah and the importance of these days? Some claim that fasting one day of these days is as fasting a whole year.And that fasting yawmut tarwiyyah grants rewards