1. Can the snapshots be copied across different Accounts (like dev,test, etc)
2. What needs to be considered for the snapshot/ec2 works seamless in cross accounts.
Following your questions:
1. Yes, you can copy EBS Snapshots from one account to another. The Snapshots however must be shared by the "owner" account to the "guest" account, before it can be copied to the "guest" account.
2. There are several factors that you need to take into account when copying Snapshots or allowing Snapshots to be used by multiple accounts, such as: region, permissions, encryption (very important if you let EBS Volumes and Snapshots encrypted by default).
For more details, you can read in the Copy an Amazon EBS snapshot article.