Hi PK,
The editing of attachments (image, audio, signature) is not currently supported in the Survey123 field app via the Inbox or Sent box. This is high on our priority list and a frequently requested feature enhancement (you will find many other posts about it if you search GeoNet). We aim to support this in the future, however a current workaround would be to use a repeat (related table) where a new attachment can be added via an add record (not edit). I would encourage you to submit an enhancement request via Esri Support, so our Support team can assign you an official enhancement number and link it to similar requests from other customers, which helps us assess demand for the enhancement and prioritize it accordingly.
Secondly, to enable the editing of repeats you need to ensure you have specified the correct bind::esri:parameter on the begin repeat question in your xlsx form. ie: "query allowUpdates=true". By default allowUpdates is false. More information can be found here: Prepare for editing existing survey data—Survey123 for ArcGIS | ArcGIS
As for your third issue regarding certain multiple choice questions, are these select one or select multiple questions and are they inside or outside of a repeat? There should be no difference with select one and select multiple questions when it comes to editing via Inbox and Sent box provided the correct parameters and settings have been used. If you are still having issues, please share your xlsx file so we can take a look.
Regards,
Phil.