Explanation
Forecasting is a feature that allows you to predict and plan the sales cycle from pipeline to closed sales, and manage sales expectations throughout your organization. Opportunity stages are the steps that an opportunity goes through as it moves from creation to close, and they determine the probability and forecast category of the opportunity. References:
https://help.salesforce.com/s/articleView?id=sf.forecasting3_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.customize_opptystages.htm&type=5

Explanation
Permission sets are a flexible way to grant additional access to users without changing their profiles. To provide access to the lead object for a team of support users, create a permission set that includes the appropriate object and field permissions for leads, and then assign it to the users.
References:https://help.salesforce.com/s/articleView?id=sf.perm_sets_overview.htm&type=5

Explanation
Expected revenue is calculated as Amount x Probability. If the expected revenue field displays incorrect values, it means that the probability associated with the stage is not accurate. The administrator should change the probability to reflect the actual likelihood of closing the opportunity at that stage.
References:https://help.salesforce.com/s/articleView?id=sf.forecasts3_expected_revenue.htm&type=5

Explanation
Lightning pages are custom layouts that let you design pages for your Salesforce org using Lightning App Builder. You can assign different Lightning pages for different apps, record types, and profiles using Lightning page assignments. To meet the requirement of displaying different Lightning pages for Accounts in Sales Console and Service Console, you need to assign Lightning pages as app default for each app.
References: https://help.salesforce.com/s/articleView?id=sf.lightning_page_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.lightning_page_assignments.htm&type=5

Explanation
The Assignment Rule checkbox is a checkbox that appears on manual case creation pages when assignment rules are definedfor cases. The Assignment Rule checkbox determines whether or not to apply assignment rules to manually created cases. If the Assignment Rule checkbox is selected by default, then any manually created cases will be assigned according to assignment rules instead of being owned by the agent creating them. To prevent this from happening, an administrator can either deselect the Assignment Rule checkbox when creating cases manually; or change the default setting for this checkbox under setup by selecting or deselecting Use active assignment rules by default.
References:https://help.salesforce.com/s/articleView?id=sf.customize_casesupport_assign.htm&type=5