You could use the following formula:
=IF(AND(LEN(Test)=12,OR(AND(CODE(MID(Test,1,1))>96,CODE(MID(Test,1,1))<123),AND(CODE(MID(Test,1,1))>64,CODE(MID(Test,1,1))<91)),OR(AND(CODE(MID(Test,2,1))>96,CODE(MID(Test,2,1))<123),AND(CODE(MID(Test,2,1))>64,CODE(MID(Test,2,1))<91)),OR(AND(CODE(MID(Test,3,1))>96,CODE(MID(Test,3,1))<123),AND(CODE(MID(Test,3,1))>64,CODE(MID(Test,3,1))<91)),CODE(MID(Test,4,1))>47,CODE(MID(Test,4,1))<58,CODE(MID(Test,5,1))>47,CODE(MID(Test,5,1))<58,CODE(MID(Test,6,1))>47,CODE(MID(Test,6,1))<58,CODE(MID(Test,7,1))>47,CODE(MID(Test,7,1))<58,CODE(MID(Test,8,1))>47,CODE(MID(Test,8,1))<58,CODE(MID(Test,9,1))>47,CODE(MID(Test,9,1))<58,CODE(MID(Test,10,1))>47,CODE(MID(Test,10,1))<58,CODE(MID(Test,11,1))>47,CODE(MID(Test,11,1))<58,CODE(MID(Test,12,1))>47,CODE(MID(Test,12,1))<58),TRUE,FALSE)
As a result, the validation runs normally:


Notice:Per my test, if we use "12" as the column name, we need to replace "Test" in the formula with "[12]".
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