How to edit in 32-bit depth. Need Photoshop?

I want to start working in 32-bit depth for black and white. I'm totally baffled by what I need to do this, and how to do it. 
Am I correct that Lightroom does nit allow 32-bit processing? If that is the case, do I need Photoshop? I was hping not to have to buy Photoshop but maybe tyhere is an affordable package of which I am not aware.

Is Photoshop only used to merge the HDR images? LR can do that right now; is that somehow insufficeitn?  If I do use Photoshop to merge, can I return to Lr for editing?

Thanks for any help.