A developer is creating an enhancement to an application that will allow people to be related to their employer. Which data model provides the simplest solution to meet the requirements?

An after trigger on the Account object performs a DML update operation on all of the child Opportunities of an Account. There are no active triggers on the Opportunity object, yet a "maximum trigger depth exceeded" error occurs in certain situations.
Which two reasons possibly explain the Account trigger firing recursively? (Choose two.)

What is true for a partial sandbox that is not true for a full sandbox? Choose 2 answers:

A developer must provide a custom user interface when users edit a Contact. Users must be able to use the interface in Salesforce Classic and Lightning Experience.
What should the developer do to provide the custom user interface?

An Apex transaction inserts 100 Account records and 2,000 Contact records before encountering a DML exception when attempting to insert 500 Opportunity records. The Account records are inserted by calling the database.insert() method with the allOrNone argument set to false. The Contact and Opportunity records are inserted using the standalone insert statement. How many total records will be committed to the database in this transaction?