SQLite database to populate dropdown lists

General information for the website: Directions and guidance
Database management system (DBMS): Other
Description of requirements/features: Requirements: SQLite database and associated html webpage with dropdown boxes populated from the database.

Four dropdown boxes. Each dropdown lists values are dependant on the choice of the value selected in the previous dropdown list, starting point from dropdown list 1. I have attached a diagram to show this. After all selections have been made a button becomes will become available which when clicked loads a new tab displaying a video corresponding to the exact choices made over the four dropdown lists. A button is also present to clear all selections.
When all dropdown boxes are clear, dropdown box 1 will have the text "Select" shown in it. The other dropdown boxes should be blank before selection and only become active after the dropdown list pervious to it has been selected. If an option is changed, for example in L2 after L3 has been set, then L3 should automatically wipe, and the list display new corresponding choices.

At the moment only one dropdown list 1 choice and variables are to be provided but we will need to be able to expand the database regularly ourselves. The number of list options can be variable, but there will only ever be 4 dropdown boxes.

The html webpage just needs to be a blank white page with the dropdowns centred and laid out like in the attached image.

Example: Select L1 Option 1 > L2 Option 2 > L3 Option 3 > L4 Option 15 > Loads 00015.avi