Explanation:

Box 1: Yes
Class extension - Method wrapping and Chain of Command.
The functionality for class extension, or class augmentation, has been improved. You can now wrap logic around methods that are defined in the base class that you're augmenting. You can extend the logic of public and protected methods without having to use event handlers. When you wrap a method, you can also access public and protected methods, and variables of the base class. In this way, you can start transactions and easily manage state variables that are associated with your class.
Box 2: Yes
In the following example, the wrapper around doSomething and the required use of the next keyword create a Chain of Command (CoC) for the method. CoC is a design pattern where a request is handled by a series of receivers. The pattern supports loose coupling of the sender and the receivers
[ExtensionOf(classStr(BusinessLogic1))]
final class BusinessLogic1_Extension
{
str doSomething(int arg)
{
// Part 1
var s = next doSomething(arg + 4);
// Part 2
return s;
}
}
Box 3: Yes
Instance and static methods can be wrapped by extension classes. If a static method is the target that will be wrapped, the method in the extension must be qualified by using the static keyword.
Box 4: No
Wrapper methods must always call next.
Note: Wrapper methods in an extension class must always call next, so that the next method in the chain and, finally, the original implementation are always called. This restriction helps guarantee that every method in the chain contributes to the result.
In the current implementation of this restriction, the call to next must be in the first-level statements in the method body.
Here are some important rules:
* Calls to next can't be done conditionally inside an if statement.
* Calls to next can't be done in while, do-while, or for loop statements.
* A next statement can't be preceded by a return statement.
* Because logical expressions are optimized, calls to next can't occur in logical expressions. At runtime, the execution of the complete expression isn't guaranteed.
Reference:
https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/extensibility/method-wrapping-coc

Explanation:

Scenario: You must install and configure a third-party solution for credit card processing within Dynamics
365 Finance. The third-party company will provide a deployable package.
You must develop a web portal that allows customers to browse products, place orders, and check order status. Product data for the web portal must be integrated as periodic batches.
You must configure the warehouse mobile device portal for warehouse operations.
You must install a third-party solution to support web portal integration. The solution is supplied as a source code model file.
Step 1: Add the package to source control and check in the changes.
Deployable packages from third parties can be manually installed on a development VM, and the installed artifacts can then be added to source control.
Step 2: Import the model into a Development environment.
Install a model in a development environment
Step 3: Synchronize the models in the Developer environment by using Get latest feature Because the models and runtime packages are in source control, other developers who use other development environments can just synchronize the models and packages to their workspace by using the Get latest feature of source control.
Step 4: Build and create a deployment package
The build process will include this runtime package in the final deployable package. This allows customers to take the deployable package from the build and have one package to deploy to their environments. The one package includes both custom solutions and all the third party solutions.
Reference:
https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/dev-tools/manage-runtime-packages
https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/dev-tools/manage-runtime- packages#deploying-third-party-code

Weight data can be maintained with a maximum of two decimals by default. If you require the ability to enter, maintain, and view weight data with a maximum precision of six decimals, you must extend the decimal point precision for the WeightBase extended data type.
Reference:
https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/extensibility/decimal-point-precision