I've a below result set.
Id Name Age
1 abc 3
Required Result:
Id 1
Name abc
Age 3
You can unpivot in a lateral join - but as mentionned by Dai in the comments, this requires casting all values to the same datatype. So:
select x.*
from mytable t
cross join lateral ( values
( 'Id', id::text ),
( 'Name', name ),
( 'Age', age::text)
) x(col, val)