Hi Munish! 
Thanks for flagging this!
Great news — this is the same root cause as another thread, and I just posted a detailed answer there. Rather than duplicate it, please check it out here:
The short version: storage/files/upload_inline isn’t the right method name for the current flow — Anna has three distinct file/upload surfaces (App upload.*, Executa host/uploadFile, and APS Files anna.files.* / files/upload_begin), each with its own permission model. The linked reply walks through which one to use, the correct capabilities, and how to validate the whole flow against the repo’s APS Files Demo example. 
Give that a read and let us know if anything’s still unclear — happy to help further! 