Dear Sir, 
Rule 10 says for the effective date of registration, what will be the effective date of registration suppose you have crossed the limit of Rs. 20 lakh on 1st June 2018 so 1st june is the date  of liability to get registered but you have applied the registration on 28th june that is within the 30 days from the liability date and certificate of registration granted on 4th july then in this case the effective date of registration is 1st june but when you fail to apply the registration within 30 days from the liability date then your  effective date of registration will be the date on which certificate is granted.
for claiming of ITC and Charging GST separate provisions will apply  i.e. Section 18, Section 34 and Rule 53.