after old Syllabus ends may 2019

no
only group 2
not both

No , U cannot write CA - IPCC exam after may - 19 under old scheme. If not cleared before May - 19 then u mandatory converted old scheme to new scheme. If u cleared any group under old scheme then u have a option to write another group (un cleared) in new scheme.

Here , If u cleared group 1 in May - 19.
For 2 nd group u mandatory to convert new scheme and u need to write 2nd group only under new scheme.

U hv to write only grp 2 under new sylbs aftr may 19.