Important Points to remember about Salesforce Sandbox Limits as per Edition:
Important Points to remember:-
1) If you need licenses for more sandboxes, contact Salesforce to order sandboxes for your organization.
2) Sandboxes don’t send email notifications when storage limits are reached.
3) You can’t Save new data/records if when storage limits are reached in Sandbox.
4) Change sets are not available to Professional Editions.
5) To check your storage limits, Goto Setup -> Storage Usage in your sandbox.
Reference – https://help.salesforce.com/articleView?id=deploy_sandboxes_limits.htm