1)
Why does the Torah change the name of the Nasi of Gad 'Elyasaf ben Deu'el' to 'Elyasaf ben Reu'el'?
1.
Ramban: It is perfectly normal for the Torah to change a name to one with a similar meaning to the original one, 1 seeing as he was called by both names. 2
1
Ramban: 'Deu'el' means that he knew Hashem', Reu'el, that he placed his thoughts on Hashem, as in Tehilim, 139:17.
2
Ramban: Another example of this is the name 'Zerach' (in Bamidbar 26:13), which the Torah changes to 'Tzochar' (in Bereishis 46:10), since both mean to shine - See Yechezkel, 27:18.