Netbeans - Ayuda con algunos problemas

Help pls
1.
Develop a program that allows you to record four grades for a list of N students, and then display these grades also calculating the average of each student, taking into account that the minimum grade obtained by each of them must be eliminated. It must also be validated that notes can only be recorded in the range of 0 to 20
2.
Develop a program that allows you to register the following data for N students: Code, First Name, Last Name, Address and Career. The entry must be made through a menu that presents the following options:

1. Data Registration
2. Data Modification (Of a student / Search key: Code)
3. Data Consultation (From a student / Search key: Code)
4. List Data (All students)
5. Exit
Considerations:

Validate that data entry is done only once.
Validate that operations 2, 3 and 4 should only be carried out if the student's data has already been registered. (Two-dimensional arrangement)
3.
Develop a program that allows you to implement the following class:

Class: Student

Attributes
String Code
String Name
String surname
String Address
String Carrera
int Cycle
Char Matricula (M = Enrolled, D = Unregistered, S = No Enrollment)
Char Status (A = Active, I = Inactive)

Methods

Create()
Modify()
Enroll()
Unregistered ()
ShowData ()

Implement at least three constructors that allow you to initialize the values of this class. After this, develop a routine to test the implementation of the class.