purchase details in gstr 4 for june 2018 quarter

since auto-population of the details of the inward supplies including supplies on which tax is to be paid on reverse charge is not taking place, taxpayers who have opted to pay tax under the composition levy shall not furnish the data in serial number 4A of Table 4 of FORM GSTR-4 for the tax periods January, 2018 to March, 2018 and subsequent tax periods.

Purchase with Reverse charge and unregistered purchase are compulsory required to be shown in gstr 4.
B2B purchase is not compulsory and no need to be shown in gstr4.   

tax liability arise or not....???
RCM is suspended on purchase from unregistered dealer ....????

Yes RCM on inward supply from URD is suspended till 30/09/2018 ,.. but services of GTA, Advocate Etc fall under section 9(3) & RCM is applicable on availing services from same