General question about solution.

[Anonymous]

Hi Team :),

I have my first task in my company. I have some basic solution, but I want to ask if I thinking good.
So, I was delegate to create flow or other solution for this scenario:

Flow should send each 1 st day of month email with congratulations of specific anniversary(3 options of anniversary: 1 year, 5 years or 10 years) to those people who are going to have one of this specific anniversary in this month.
Emails should include specific 3 options to choose as a gift, for specific anniversary: 
1 year anniversary:
Option 1
Option 2
Option 3
5 years anniversary:
Option 4
Option 5
Option 6
10 years anniversary:
Option 7
Option 8
Option 9
When employee choose option, I need to save this information on sharepoint list for HR department to overview.
When employee don't choose any option, I should save first option as a default. 

Second case is that I probably need another flow which will be updating sharepoint list with employees from 2 excel files. 
HR department wants to give me one excel file with 300 employees, and delivering 2 different excel file with new hire employees and employees which are leaving our company at specific month, before when month ends. So first I need to create main sharepoint list from excel file and updating this list each 25 th day in each month before I send email to specific employee which have anniversary.

Sources:
Excel file with 300 employees
Excel file with new hire employees 
Excel file with employee who are leaving 

What I did:
Sharepoint list with employees and hire date, 1 year, 5 years, 10 years anniversary date
Sharepoint list with full name and choosed option form email
Basic flow for sending anniversary email
Basic flow for updating sharepoint list with employees

Question is what will be the best tool for give employee options to choose specific gift in email and save this info somewhere?
Is impossible to create one flow for this scenario?
What should I care about? Some specific validation? Some corner cases like what if first of month will be at Sunday?

I uploaded screen of this what I made. 
Right now I have problem with:
-delete leaving employee from sharepoint list(when received excel file with leaving employee),
-send email to specific employees for specific anniversary(right now flow sending email in exactly day when employee have anniversary)
-don't find solution to receive answer from employee or default option when specific time gone(for example 1 week)

Sorry for very long questions.