Cancelled PO Lines or partially closed lines

Cancelled PO Lines or partially closed lines - cannot be reopened because they are at next Status at 999. However for the remaining approved funds I can go into the same PO and enter another line with the balance of that PO which was partially received and probably closed by mistake. this was a 2 way match.The other 2 lines were cancelled at the PO Level. SO in Test env I re-entered the 3 lines and it routed for approval. is that possible to do and what are the factors we have to keep in mind.  ...Please advise

They also have a 2000 in tolerance for Function type 3 in tolerance setup. which is at Release /Convert which I believe is for Blanket release time and converting Reqs into PO time ( is this correct)?...thanks