Data Type Consistency CASE / Decode?

Data Type Consistency CASE and Decode

CASE expects data type consistency, DECODE not expecting.

Obviously both functions handling data types are different let it be

SQL> select decode(2,1,1, 2,'2', ' three' )"RESULT" from dual;

RESULT
---
2
SQL> select case 2
2 when 1 then 1
3 when 2 then 2
4 else 3
5 end "RESULT" from dual;

RESULT
2
SQL> select case 2
2 when 1 then 1
3 when '2' then 2
4 else 3
5 end "RESULT" from dual;

ERROR at line 3:
ORA-00932: inconsistent datatypes: expected NUMBER got CHAR

know cause of error here????I mean " every time case exp checking data type consistency"

my thought is

I am trying to get same output but different methods. Yes, clearly states this is one of the Oracle bug!

I want to know how oracle handles here ???? i mean 3rd query.Purely i am testing this function with dual(dummy) table...
obviously, no possibilities for different data type.next one i am not sure about Oracle compares int variables to int variables, char variables to char variables,

I think so .... that's why oracle throws error. am i right ??ORA-00932: inconsistent datatypes: expected NUMBER got CHAR

see this query

SQL> select case 2
2 when 1 then 1
3 when '2' then 2
4 else 3
5 end "RESULT" from dual;

// clearly i am stating what's error on 3rd line ?????Even if I refer reference books some concepts are blind to understand.