Can I tip the ball with an open hand?

No. In beach volleyball it is an attack-hit fault to complete an attack hit (Rule 13.2.3):

• with an open-handed finger action (a dink or tip with soft fingers); or
• with fingertips that are not rigid and together.

What you can do instead:

• Poke: play the ball with fingertips that are rigid and held together.
• Overhand pass over the net: only if the ball travels perpendicular to the line of your shoulders (Rule 13.2.5). The exception is a genuine set to your team-mate.

Other attack rules (Rule 13):

• Any player may attack at any height, as long as contact is made in their own playing space. There is no front-row or back-row distinction.
• You may not complete an attack hit on the opponent's serve when the ball is entirely above the top of the net.
• Hitting the ball in the opponent's space, or hitting it out, is a fault.