Alterations to the base code of a Drupal Open Source Project

I have a few fields in a Drupal open source Learner Management System that I need them validated and some drop down lists filtered according to user choices: User profile. User can register on the system, create own account and they can onetime link with embedded password. Upon login with onetime link, I need the user to just change password and when done, edit own profile. 2 Types of users needed in the system Learner/Student, Employer/Training Manager and Admin. Each user has roles which are already defined. But I need Learner/Student and Employer/Training Manager to have different profiles. Another are filed related: Here is the logic: Field = Date of Birth must be derived from ID number. South African Identity numbers have Date of birth imbedded in them. Example: (ID Number: 7904285450089) Date of birth is the 1st six digits. In this case the logic is: add 19 to 79 and it becomes 1979/04 (April)/28 (date in April). I need some Javascript/Jquery or whatever script to auto fill the Date of Birth field derived from ID number. Another example: (ID Number 0004285450089), Date of Birth is the 1st six digits. In this case the logic is: add 20 to 00 and it becomes (2000/04 (April)/28 (date in April). That's the initial requirement. Auto filter: Province - Municipality - Town is how South Africa is divided government wise, like the US has State, County, city, etc. Here the logic is, if I select a Province, filter Municipalities according to those belonging to the Province and then Filter Town according to those belonging to that Municipality. This is to minimize entry errors. I have a list of provinces, municipalities and town in a spreadsheet with their respective relationships. I just need to have them linked and auto filtered based on user selection. I have the values of the drop down lists and relationships, just need them auto filtered as the user chooses. Then comes field = Learning Pathway field. This field depends on another field called Employment Status. If status is unemployed, only certain learning pathways should show (The field's contents and the conditions is available in excel spreadsheet. If employed same thing, certain Pathways appear). Then on the user profile, there is Learner Status, These I need additional statuses added to this field. We have 2 now, I need 4 more added to the list and admin and some user role able to change this but not the authenticated user themselves. There is the export learner function (within the same system). This is the function that exports users out of the system into excel. Currently it exports only usernames, I need the export function to have more details, username, name, surname, ID, learning pathway, etc. Lastly, there is a "add multiple learners" to the list for them to have details. Here are the links: [login to view URL], I need to add more details to the selection (Name, surname, highest qualification, career choice, learning pathway) and ability for the user to filter what type of learners to add to the group. [login to view URL] export list also to have the same details as adding multiple learners. These all to make system functionality a bit more pleasant to the client.