SQL Server 2019

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create table tbl
(
    Product varchar(2),
    StartPoint char,
    EndPoint char
);
insert into tbl values
('P1', 'A', 'B'),
('P1', 'B', 'C'),
('P1', 'C', 'D'),
('P1', 'D', 'E'),
('P1', 'E', 'F'),
('P2', 'P', 'Q'),
('P2', 'Q', 'R'),
('P2', 'R', 'S'),
('P2', 'S', 'T');
9 rows affected

declare @col_count int;

select  @col_count = max(cnt) + 1
from
(
    select  Product, cnt = count(*)
    from    tbl
    group by Product
) t;


declare @sql nvarchar(max),
        @col_1 nvarchar(1000),
        @col_2 nvarchar(1000);
        
with cols as
(
    select n = 1
    union all
    select n = n + 1
    from   cols
    where  n < @col_count
)
select @col_1 = string_agg(quotename(n) + ' AS ' + stuff(quotename(n), 2, 0, 'PP'), ','),
       @col_2 = string_agg(quotename(n), ',')
from   cols;

print @col_1;
print @col_2;

select @sql = 
N'with rcte as
(
    select Product, t.StartPoint, t.EndPoint, path = 1
    from   tbl t
    where  not exists
           (
               select *
               from   tbl x
               where  x.Product = t.Product
               and    x.EndPoint = t.StartPoint
           )
           
    union all
    
    select t.Product, t.StartPoint, t.EndPoint, path = path + 1
    from   rcte r
           inner join tbl t on  t.Product    = r.Product
                            and t.StartPoint = r.EndPoint
)
select Product, ' + @col_1 + '
from
(
    select Product, Point = StartPoint, path
    from   rcte
    
    union all
    
    select Product, Point = EndPoint, path + 1
    from   rcte r
    where  not exists
           (
               select *
               from   tbl x
               where  x.Product = r.Product
               and    x.StartPoint = r.EndPoint
           )
) d
pivot
(
    max(Point)
    for [path] in (' + @col_2 + ')
) p'


print @sql

exec sp_executesql @sql


Product
PP1
PP2
PP3
PP4
PP5
PP6


P1
A
B
C
D
E
F

P2
P
Q
R
S
T
null


[1] AS [PP1],[2] AS [PP2],[3] AS [PP3],[4] AS [PP4],[5] AS [PP5],[6] AS [PP6]
[1],[2],[3],[4],[5],[6]
with rcte as
(
    select Product, t.StartPoint, t.EndPoint, path = 1
    from   tbl t
    where  not exists
           (
               select *
               from   tbl x
               where  x.Product = t.Product
               and    x.EndPoint = t.StartPoint
           )
           
    union all
    
    select t.Product, t.StartPoint, t.EndPoint, path = path + 1
    from   rcte r
           inner join tbl t on  t.Product    = r.Product
                            and t.StartPoint = r.EndPoint
)
select Product, [1] AS [PP1],[2] AS [PP2],[3] AS [PP3],[4] AS [PP4],[5] AS [PP5],[6] AS [PP6]
from
(
    select Product, Point = StartPoint, path
    from   rcte
    
    union all
    
    select Product, Point = EndPoint, path + 1
    from   rcte r
    where  not exists
           (
               select *
               from   tbl x
               where  x.Product = r.Product
               and    x.StartPoint = r.EndPoint
           )
) d
pivot
(
    max(Point)
    for [path] in ([1],[2],[3],[4],[5],[6])
) p