Hi Zain
SAP is designed like that and it has a reason
Many organizations don't create the Final Asset Master while creating the Purchase Order.. So, all their asset purchases are first made in an AUC Asset, which is then settled to the Final Asset at the end of the month
Hence, SAP allows you to raise multiple PRs against same asset
For any custom checks, you can use BADI ME_PROCESS_REQ_CUST
Hope this helps
Regards
Ajay M