XLSform - Put a constraint on the date of birth - Focal point - Vulnerabilities

For Q2 which is

Solution is on this link: Date check or constraint - #2 by iamnarendrasingh

For Q3 which is

Solution is here Constraints on date and age - #7 by M_A_Serge_SOMDA

Check both these links, these might be helpful for you.

Best,
@iamnarendrasingh