1.Do not allow special characters, Allow only characters, digits,spaces.
2.Actual field(Text) length is 40 but we need to write if the field__C value is 'abc' and 'bcd' any one of value matches length should be 32 characters

Handeling validations -
1.validation should trigger only User cpq pilot check box is true 
2.Validtion should trigger only cpq permissions set assigned users. 
 

Condition -1
if pilot__c check box is true then only trigger
condition 2
Trigger only cpq permissions assigned to that user.
Condition -3
It allows -characters, digits, spaces, number
not allow-special characters
Restrict- no of characters 32


Awaiting for best answer.