Which aspect of Apex programming is limited due to multitenancy?

A developer considers the following snippet of code: Boolean isOK; integer x; String theString = 'Hello'; if (isOK == false && theString == 'Hello') { x = 1; } else if (isOK == true && theString =='Hello') { x = 2; } else if (isOK != null && theString == 'Hello') { x = 3; } else { x = 4; } Based on this code, what is the value of x?

A developer needs to apply the look and feel of lightning experience to a number of applications built using a custom third-party javascript framework and rendered in visualforce pages which option achieves this?

What is a capability of the Developer Console?

Which code in a Visualforce page and/or controller might present a security vulnerability?