Application properties can be defined in .yaml or in .properties file.
MuleSoft Doc Ref : https://docs.mulesoft.com/mule-runtime/4.3/configuring-properties#supported_files

lookup(String,Any, Number)
This function enables you to execute a flow within a Mule app and retrieve the resulting payload.
It works in Mule apps that are running on Mule Runtime version 4.1.4 and later.
Similar to the Flow Reference component (recommended), the lookup function enables you to execute another flow within your app and to retrieve the resulting payload. It takes the flow's name and an input payload as parameters. For example, lookup("anotherFlow", payload) executes a flow named anotherFlow.
Correct answeris
lookup( "createCustomerObject", {first: "Aice, last: "Green"})
MuleSoft Documentation Reference : https://docs.mulesoft.com/mule-runtime/4.3/dw-mule-functions-lookup

Scatter-Gather Router
The Scatter-Gather component is arouting event processor that processes a Mule event through different parallel processing routes that contain different event processors. Each route receives a reference to the Mule event and executes a sequence of one or more event processors. Each of these routes uses a separate thread to execute the event processors, and the resulting Mule event can be either the same Mule event without modifications or a new Mule event with its own payload, attributes, and variables. The Scatter-Gather component then combines the Mule events returned by each processing route into a new Mule event that is passed to the next event processor only after every route completes successfully.
The Scatter-Gather component executes each route in parallel, not sequentially. Parallel execution of routes can greatly increase the efficiency of your Mule application and may provide more information than sequential processing.
Mule Ref Doc : https://docs.mulesoft.com/mule-runtime/4.3/scatter-gather-concept

Correctanswer is [[5, 10, 15, 20], 5]
Key thing to note here is that any changes made to payload in for each loop are not available outside for each scope where as variable value updated in for each loop is visible out side for each loop too.
In this example , sequence can be described as follows
1) Payload is set to the value [5, 10, 15, 20]
2) Variable is set to the value of 1
3) For each loop is executed four times and in each loop payload value is updated to append "Req" and variable is count is increased by 1
4) Once control comes out of for each , payload changes made within for each are not visible. Hence payload at this point of time is equal to payload available before entering for each loop which was [5, 10, 15, 20].
Similarly variable value updated in for each loop is also available outside hence variable value is 5 as it was updated in loop.
5) Hence correct answer is [[5, 10, 15, 20], 5]
For Each Scope
The For Each scope splits a payload into elements and processes them one by one through the components that you place in the scope. It is similar to a for-each/for loop code block in most programming languages and can process any collection, including lists and arrays. The collection can be any supported content type, such as application/json, application/java, or application/xml.
General considerations about the For Each scope:
By default, For Each tries to split the payload. If the payload is a simple Java collection, the For Each scope can split it without any configuration. The payload inside the For Each scope is each of the split elements.
Attributes within the original message are ignored because they are related to the entire message.
For Each does not modify the current payload. The output payload is the same as the input.
For non-Java collections, such as XML or JSON, use a DataWeave expression to split data. Use the Collection field for this purpose.