RL: G1 humanoid arms control

[lambdavi]

Hello everyone, I am having trouble in creating an RL environment for the Unitree G1. I would like to create an environment to pick a cube from the table. I am confused though on how to control only the arms while keeping the other joints fixed.
Do i have to control all the joint or is there a way to keep the torso and lower legs fixed and focus on the arms/hands commands?