How to have nested grabs?

How can I get nested grabs?

I am new to VR. I havent yet started using VRTK. I wanted to know how I can implement something like this on my own.

Also, as someone who's really new, can some explain to me how are all these different, i.e steamVR/vrtk/unity's own vr solutions and the occulus implementation package.

Im currently using the occulus's implementation stuff and I feel really overwhelmed by everything else around.