2)
Wouldn't it be better to create one table only for renting issues and store all the "add rental request" data which are connected to the vehicle instance by the vehicle ID field located in another table?
Then one doesn't need the rental request folder, the order folder and the rent table anymore. you create just a "Rent" Folder.
From the practical side of view, for the person who manage all the rentals, it would be better to see all rentals in one list (means: one view). Then it would be also possible to see a history.

As for instance:
Fields:
|ID| |ID of the linked vehicle| |Titel| |Name of customner| |amount| |Total Price| |Rental from| |Rental to| |Pick Up Location| Drop Off Location| |Status of booking| |status of payment| and other fields ...

The status field of booking should show the selectable fields:
- request (--> booking request)
- confirmed (--> booking confirmed by admin)
- picked up (--> the customer has picked up the car)
- returned or completed (--> the customer has returned the car)
- canceled (--> admin or customer has canceled)
- service (-->the car is in the service and not bookable)

It would be also much easier to church for vehicles which are rented out or which will come soon back to a specific rental station. And also one can see, if one sort the fields, which rentals get returned today and which rentals start today.

Sorry, If you check Database Normalization - is not good save all data in 1 table.
Best if data group with common specific.
Rent request - 1 features
Rent - other
order - next features.

Also in our Joomla car software

also You may, move car to rent - without rent request.
and not always - you ask money for rent, so tables - orders may no need for you.

Also you may not only rent - you may sell cars, so table with order need connect also with BUY requests

Regards
OrdaSoft team