How to split string in PostgreSQL to make combination with another string

The is a very "unstable",like sitting on a knife edge and could easily fall apart. It depends on assigning values for each delimited value and then joining on those values. Maybe those flags that are known to you (but unfortunately not us) can stabilize it. But it does match your indicated expectations. It uses the function regexp_split_to_table rather than unnest to split the delimiters.

with base (num, list) as 
   ( values (1,'IceCream#Chocolate#SoftDrink')
          , (2,'Amul,Havemore#Cadbary,Nestle#Pepsi')
          , (3,'Party#Wedding')
   )  
   , product as
     (select p, row_number(*) over() pn
        from ( 
              select regexp_split_to_table(list,'#') p
                from base
               where num=1
             ) x
     )
   , maker as
     (select  regexp_split_to_table(m, ',') m, row_number(*) over() mn
        from (
              select regexp_split_to_table(list,'#') m
                from base
               where num=2
             ) y
     )
   , event as
     ( select regexp_split_to_table(regexp_split_to_table(list,'#'), ',') e
         from base
        where num=3
     ) 
select p as product
     , m as maker
     , e as event
  from (product join maker on pn = mn) cross join event e
  order by pn, e, m;

Hope it helps.