Can same assignment be assigned to different work queues?also is there a restriction to number of assignments assigned?-no

In Pega, an assignment is typically routed to one operator or one work queue at a time.
So a single assignment cannot simultaneously belong to multiple work queues. However, you can achieve similar behavior by Re-routing the assignment from one work queue to another

Usually no — a guardrail warning is not a hard stop to. Pega gives guardrail warnings when a flow/process has too many steps/shapes because very large flows become:

  1. hard to maintain
  2. difficult to understand
  3. harder to test
  4. potentially less performant