As regards the stock valuation
Difference between closing stock is recognised as difference. Credits represent cl stk credited to the P&L
Under FIFO the last purchases remain outstanding & hence value is more whereas in LIFO it d b the opposite.
Say for 2nd yr, cl stk as per FIFO is 131 & as per LIFO is 21. The difference in profit of 110 is considered for FMP due to method change as that is the extent of excess credit to P&L attributable to the method change.