magento2 – Edit Customer Address Field To Accept Custom Format

I am developing using Magento2.3.5-p2 on Ubuntu 20.04

I am required to edit the customer account details as per below

enter image description here

Description of the above image is as below

  1. The first and last name will be merged and the field input will appear as Full Name like above

  2. Contact Numbers are as stated in the image above

  3. Postal Code are as stated on the image above

  4. State is dimmed and cannot be changed, once postal code has been added the value on this field is auto-filled

  5. City is dimmed, only when a postcode is added it is auto-populated and the customer able to select which city

  6. Full addresses are to be changed as shown on the image above

The data setlist for the state and city under the postcode is available already through API call

I am thinking of developing this using Jquery and Ajax

but I am having a problem estimating how long will this development takes,

I am thinking like 5 days due to

  • copy and modify frontend codes
  • copy and modify backend codes and extend
  • update the frontend layout
  • update the backend processes
  • update the data validation
  • add in Jquery and Ajax
  • add in Helper to call postcode
  • making sure the process edited fully reflected on Registration, Customer Account, Customer Address, Checkout Page

do help guide from an expert on what is the best way to do this ( like if there is even better ways that can be done like through admin configuration for example )