Q. Can a person lift their hands and make dua at the cemetery?

A. Yes provided the hands are lifted without the intention of one praying to the dead

We pray to Allah (Subhanahu Wata’Ala) not the man/woman in the grave

Best to turn oneself away from the deceased, so as to not create a resemblance of one praying to the dead

If one cannot change direction due to the crowd, then one can also make dua with the hands upon the sides so as to avoid  resemblance to praying to the deceased.

Allah Certainly Knows Best.