Compare column(B,C) values for each specific value in column A

Hi Dear Excellers
I need a formula to compare the values of column B,C and D using column A as reference

Excel file attached
More Details

for example for 1_26679 value in column A ---> is all the values in column B are equal
1_26679 value in column A ---> is all the values in column C are Equal
1_26679 value in column A ---> is all the values in column D are Equal
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1_26680 value in column A ---> is all the values in column B are equal
1_26680 value in column A ---> is all the values in column C are Equal
1_26680 value in column A ---> is all the values in column D are Equal
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And So on ....