Create test table

create table listagg_test(a number generated by default on null as identity  
 ,grp  number  
 ,name varchar2(50))

 insert into listagg_test (grp, name) values (1,'Lemar')

 insert into listagg_test (grp, name) values (1,'Einstein')

 insert into listagg_test (grp, name) values (1,'Turing')

 insert into listagg_test (grp, name) values (2,'Kepler')

 insert into listagg_test (grp, name) values (2,'Lovelace')

 insert into listagg_test (grp, name) values (4,'Eugenie')

 insert into listagg_test (grp, name) values (4,'Novella')

 insert into listagg_test (grp, name) values (4,'Novella')

 insert into listagg_test (grp, name) values (4,'Tyson')

 insert into listagg_test (grp, name) values (3,'Zappa')

 insert into listagg_test (grp, name) values (5,'')

Group by SQL

select grp  
   ,count(*) cnt 
   ,listagg(name,', ') within group (order by name) names  
   ,Min(name) KEEP (DENSE_RANK first ORDER BY name) first_name  
from listagg_test   
group by grp

Row level analytics

select t.*   
  -- inline view required to split secondary names?  
  ,listagg(case when rank_person_group != 1 then name end,', ')     
       within group (order by rank_person_group)  
       over (partition by t.grp) secondary_names  
from (  
select a, grp, name -- standard columns  
   -- unique names overall  
   ,count(distinct name)   
     over () cnt   
   -- names by group  
   ,count(name)   
      over (partition by grp) cnt_group   
   -- rank names within group  
   ,dense_rank() over (partition by grp order by name asc) rank_person_group  
   -- allocate unique number to each name  
   ,row_number() over (order by name asc) number_person  
   -- aggregate names  
   ,listagg(name,', ') within group (order by name)   
     over (partition by grp) names  
   -- show first name only  
   ,min(name) keep (dense_rank first order by name)  
     over (partition by grp) first_name  
   -- alternative method, tweaked for last name  
   ,first_value(name)  
     over (partition by grp order by name desc) final_name  
from listagg_test  
)  t