Odoo 15 CE Customization

Hi,
We want to perform below changes in Odoo:
- Add field for location in sales order
- Show location and sales order for each line in the invoice, in view mode and we must be able to use it in pdf template.
- in printed invoice we want to show only total amount for the order in each line without breakdown
- Add module for attendance, from this module the HR Employee will upload excel with below columns:
Employee ID, Employee Name, Date, Normal Hours, OT1 (Over Time 1) Hours, OT2 (Over Time 2) Hours, Absent Hours.
- Total hours (Normal, OT1, OT2) cannot be more than 24 hours and absent hours can not be more than 8
Each employee will have hourly rate in his profile
- From payroll we want to define formula and use uploaded details to calculate the salary.
- Formula will be like this
Salary = Basic Salary + OT1(Total overtime1 ) Normal Hourly Rate 1.25 + OT2 OT1(Total overtime2 ) Normal Hourly Rate 1.5 – Absent* Normal Hourly Rate
We must have flexibility to change the formula as current one(e.g. like adding expenses and allowances)