You are in error. The same Greek
word ( 'beginning'; Strong's #
746 ) is used in both verses. It is the 'grammar of the language' that makes the difference...
The
word 'beginning' means the same thing in both verses:
"the
commencement ( beginning / orgin ) of the creation of God"
Mark 10:
[SUP]6[/SUP] But from the beginning of the creation God made them male and female.
This verse is saying:
"But
from [ the time of ] the beginning of the creation of God..."
i.e. - since the beginning of the creation of God
Revelation 3:
[SUP]14[/SUP] And unto the angel of the church of the Laodiceans write; These things saith the Amen, the faithful and true witness, the beginning of the creation of God;
This verse is saying:
"These things saith the Amen, the faithful and true witness, [ who is ] the beginning of the creation of God;"
i.e. - the author ( source ) of the beginning of the creation of God