is it ok i skip the 2.3 and 2.4 question in the form?

i dont answer the 2.3 and 2.4 in the application form because i dont know my date of first entry and dont know how long i stay there,because my inviter told me my visa is valid for 3 months but the extension is no problem...he already book a flight for me next month june 15.is it ok i skip the 2.3 and 2.4 question in the form?thank you in advance...