Here are a couple of concepts that might help in achieving the creation of receipt (2 step) for transfers

Firstly you would need to unarchive the location Inter warehouse transit location. This is to ensure transfer is happening in 2 steps to be able to track with 2 operations.

Couple of ways to create routes
1. Push rules - create a push rule
From transit location to WH-B/ stock 
This would create a receipt in WH-B when any product is moved to transit location 

To make a transfer, create internal transfer from WH-A to transit location on validation of this transfer a receipt operation would be created in WH-B

This is in line with your example of sending oranges from A to B. 
The limitation with this rule is that you wouldn’t be able to use the transit location to move products from WH B to A

2. Pull rule - Define a route using pull rules

Pull from Transit to WH-B

Pull from WH-A to Transit

Apply this to product or product categories.

To make a transfer create a replenishment in WH-B with this route, (order once). It should create 2 operations.
Limitation is that you would have to create replenishment by individual  product.

3. Another option could be to have one warehouse resupply the other.

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Additional resources

The video below addresses a couple of business cases and details the steps to achieve them. It might help in applying and creating the routes (push/pull, triggers etc) specific to your business needs.
https://www.odoo.com/slides/slide/superstar-logistic-solution-1103?fullscreen=1

Hope this helps you in defining the use case specific to your needs.

In Odoo 16, you can create a 2-step internal transfer process by using the "Planned Transfer" functionality. With planned transfers, you can create a transfer order in Warehouse A and then process it as a receipt in Warehouse B.

To create a planned transfer, follow these steps:

Go to the "Inventory -> Operations -> Planned Transfers" menu.
Click on the "Create" button to create a new planned transfer order.
Select the source location (Warehouse A) and the destination location (Warehouse B).
Add the product that you want to transfer (oranges) and specify the quantity (5).
Save the planned transfer order.

Once the planned transfer order is saved, it will appear in the "Receipts to Process" section of the Warehouse B inventory overview. The staff in Warehouse B can then process the planned transfer order as they would normally do when receiving goods from an external vendor.

To disallow over-transferring, you can enable the "Allow negative quantities" option in the inventory settings. To do this, follow these steps:

Go to the "Inventory -> Configuration -> Settings" menu.
Scroll down to the "Inventory Valuation" section.
Deselect the "Allow negative quantities" option.
Save the changes.

With this setting enabled, you will not be able to confirm a transfer order if it results in a negative inventory balance in the source location.

Question 2 should not be able, I've just tested it and it did not allow me... I dont know how you did it... Any customs?

About question 1 I need more info to help you.