I have a professional edition org and i want to set sharing rules on Opportunity Object  which is not available. Hence i am looking to go for Apex Managed Sharing. Would it work . If yes please help me with the solution.

Its urgent

Created a new Custom object ,now i want to create this Custom Object as Tab in the App ,but when i create a "Lightning App",can't see the Custom object in Navigation Items,I checked in profiles as well ,i had full access to the custom object as i am salesforce admin


Your help is highly appreciated

Fiona