1a. The Rig-Veda is an ancient Indian Vedic text which contains hymns in Vedic Sanskrit, which is an ancient Indo-European language. It also has additional information on liturgy, ritual, and mythical exegesis. There are 1017 hymns.

1b. The Yajur-Veda was primarily used for worship purposes and is also in Vedic Sanskrit. There are 1,875 verses.

1c. The Sama-Veda is mostly composed of songs and chants and was written in Vedic Sanskrit. There are 1,549 verses.

1d. The Athar-Veda is the latest scripture and has information on every day life. There are 730 hymns.

2.  Indulgences were something you could buy for a family member who had died that will get them out of purgatory.

3.  I think he saw it as a scam and it was just a way for the church to get more money.

Source: https://en.wikipedia.org/wiki/Indulgence

4.  The Hajj is a pilgrimage to Mecca, the holiest city to Muslims, that takes place every year over the course of five days. It is to show there submission to Allah (God) and about two million Muslims participate.