GST cancellation

hi, query pertains to someone who is a real estate agent. the details are as follows.

1. the person, an individual got GST registration done in July 2019
2. his turnover is below 20 lakhs until today i.e august 20, 2019. Until June he had a total turnover RS 8 lakhs.
3. no GST invoice has been raised till date after June end since no services were rendered.
4. now this person is expecting a cheque of RS 20 lakhs against a deal but does not want to pay GST. he will split the cheque with his wife indicating her as a separate broker and the client is ready to issue two cheques of RS 10 lakh each.
5. this person since he is already registered under GST will have to charge gst on the invoice of RS 10 lakhs, GST will be 1.8lakhs on this 10lakhs. total = 11.8lakhs
6. but since the client, who is an individual does not want to pay gst, he is saying the amount of RS 10lakhs should include GST.
7. the property dealer wants to cancel the registration so that he does not have to pay the GST. his total turnover will be 10lakhs + 8 lakhs = 18 lakhs.

questions
a. can the property dealer cancel the registration and then raise an invoice for RS 10 lakhs. in such a case he will not be liable to charge gst.
b. can he reapply for GST later in the year when the turover exceeds 20 lakhs.

the basic idea is to avoid paying GST on the invoice of RS 10 lakhs out of his own pocket. since the property dealer is registered under GST as of now and his client is not ready to pay GST, this 10 lakhs will be deemed to include the GST amount of 18%. the dealer wants to avoid this GST liability by cancelling the registration and then raising an invoice at a later date. thanks