everything mixed in here.
Perpetual inventory is a inventory method of warehouse management - but this is in MM space.
Perpetual inventory is much different from what you described above, please have a look into the docu of: Physical Inventory: Methods
The transaction you mentioned is actually cycle counting, which is used if you have a low inventory accuracy and want count certain items more often.
You have no real control over cycle counting, I explained it in detail in probably 20 or more discussions in SCN.
It is certainly not meant to count the different classification separate from each other. And it is not possible to restrict the proposal to just 50 items per month, except you do define this outside in SAP and upload the material numbers via multiple selection in MICN.
Automatic creation of inventory documents....I recommend to read my blogs: Physical Inventory is more than just SAP..