Is it true that there is an inscription of Yahweh found that is older than when Moses was revealed the name of God in the Bible?
Tradition holds that Moses lived sometime around the 15th century B.C. This would put the oldest use of the tetragrammaton (the Hebrew word "YHWH", anglicized to "Yahweh") to the same time frame, as Moses wrote the oldest portions of the Bible.
Outside the Bible, the oldest known inscription of the tetragrammaton appears on the Mesha stele, which has been dated to around 840 B.C. You can read more about the Mesha stele here.
In a tomb at Ketef Hinnom in Israel, the oldest text of the Hebrew Bible was discovered. The text, inscribed on a silver scroll in the old Hebrew script dating to the 7th Century B.C., is the Aaronic blessing (Numbers 6:24-26), which begins, "yeverekh'kha YHWH Vayishmarekha" (May Yahweh bless you and keep you). Source: http://ancient-hebrew.org/bible_manuscripts.html
The oldest known inscription of the Tetragrammaton dates to 840 BCE, on the Mesha Stele. It bears the earliest certain extra-biblical reference to the Israelite God Yahweh. The most recent discovery of a Tetragrammaton inscription, dating to the 6th century BCE, was found written in Hebrew on two silver scrolls recovered from Jerusalem. Source: https://en.wikipedia.org/wiki/Tetragrammaton
I found a related questioninBible Hermenutics: https://hermeneutics.stackexchange.com/questions/14042/the-name-of-god-in-ancient-manuscripts
You may find it helpful.