If I get what you are asking, here is a possible way of doing it.
with AdvanceCnt as (
select
EmployeeId,
RequestedOn,
row_number over(partition by EmployeeId order by RequestedOn) rowid
from AdvancePayment
where RequestedOn
)
select
e.EmployeeId empId,
e.FullName Name,
ac1.RequestedOn [1st advance date],
ac2.RequestedOn [2nd advance date]
from Employee e
inner join
(select * from AdvanceCnt where rowid = 1) ac1
on e.EmployeeId = ac1.EmployeeId
left join
(select * from AdvanceCnt where rowid = 2) ac2
on e.EmployeeId = ac2.EmployeeId
;
The query has not been tested, but hopefully it will help you out.