Hi @LeesVisuals,
Thanks for the question!
You can't edit the topology inside Substance 3D Sampler, but nothing prevents you to send the model to Blender, or any 3D modeling software to delete the undesired parts.
Considering the Material section of the export not available, I've saw your previous thread, and I just want to check certain conditions to be sure I'm giving you the proper answer.
You'll find many 3D viewers for smartphone on the AppStore or Google play store. From there you'll only have to send the 3D asset to your phone in order to display it within the app. Alternatively, you can use Substance 3D Stager to publish your scene on the web and display it from your Smartphone (I've never tried to open the link from my phone, but I'm pretty sure this should work). I know Marmoset Toolbag 4 also have a similar feature.
Regards,