RE: hide leads and opportunity from other BU users
Hi Irfan,
It is not possible to restrict the users access for any specific BU. As suggested by others, you can set BU level access to restrict user to access records from their own BU.
In your case, you can create 2 security role say "Sales Manager Global" & "Sales Manager Local".
In "Sales Manager Global" , you can set the org level privledges for all your required
entities (leads, opportunities etc)
In "Sales Manager Local" , you can set the BU level privledges for all your required entities (leads, opportunities etc)
Now, you assign "Sales Manager Global" security role for top BU [User who needs to have access to all records]
and assign "Sales Manager Local" security role for child BU [User who should not see records from other BU]