"1. Is there any option to mass delete physical Inv documents?"
Yes.
You can delete the Physical Inv Documents with MIAD but for that you need to maintain one variant with it and copy all the Document no. in TEXT file paste in the in Archiving Selection's.
The tcode steps are as follows:
MIAR - Archive Physical Inventory Documents
MIAD - Delete Physical Inventory Documents
MIAV - Manage Physical Inventory Document Archive
"2. How can I know if the physical inventory documents are posted (MI07) or not yet?"
Please check ISEG table and provide the time Period as
search menu so that you can see all the Doc's posted on today's date.
"3. If I see any material document of mov type 701 or 702, there is no reference of physical Inv Doc # in it. How can I know that this material document is created as a result of which physical Inv document?"
Go to MB59 and check the Material documents with respect to Movement type and date.
The difference you will see in MMBE as per the movement used.
