Guts have try using it to summon 5 gods hand, but he cannot use it, because when behelit come to human world, the owner have destined.
There are two rules to using one in its intended way
1. the need/want 2. a desire that has been utterly destroyed.
Even if the Behelit belongs to a future Guts who manages to remove
the brand and regains his humanity he wouldn't have been able to
us it since condition 2 wasn't met.
And in the end we don't know who it belongs to also about the destined owners...
... that's something that needs another perspective after seeing what SK did
with them meaning Betchi might be a weapon and isn't to be used in the
the classic sacrificing way.
Guts will never become Immortal (like SK), because SK is former branded that "swallowed" by Berserk Armor and lost his humanity.
Him being a former branded we don't know that for sure do we?
He might be an apostle who turned against the God Hand cause
if he had the brand he doesn't seem to have it any longer so
how has he lost it through using the Berserker Armor?
Maybe he was neither just a man who lost his Kingdom and
turned to magic to fight Void.
(Who might have been the wise man imprisoned in the Tower of Conviction.)