1.What do you mean by a validation Rule.

Ans: A validation rule is some set of conditions. If the condition gets satified, then it gives error.

2.What are the Types of Validation Rules.

Ans:
A] System Validation Rule    (Salesforce Default)
B] Custom Validation Rule   (Developer Created)

3. What is validation rule governor limits.

Ans:

Note - Generally in then Company, we use Unlimited Edition etc., and not use Developer Edition.

4. Does Validation rule works for Delete operation

Ans: No. Not Possible. Works only for Create and Update operations.

5. Using Validation rule, How to prevent Account record deletion, if Rating is Hot.

Ans: Validation Rules cannot prevent record deletion in Salesforce — they only work when creating or editing records.
Solution:
A] User Lightning Record Triggered Flow (Delete event with custom error)
B] Use trigger (Apex Trigger) on Account's before delete event.

6. Can we Bypass a validation rule?
I have created a validation rule, which prevent Account Record insert/update, when its Rating is Hot. So, when I manually create the Account record with Rating Hot, it is giving me Error, which us perfectly fine. Okay?
Now, when I upload Account records using Data Migration Tools (e.g Data Loader / Workbench) with Rating Hot, it should allow me. Means validation rule should not give me error. How can you achieve this.

Ans:sYes, it is possible.
A] Create a Checkbox field on Account, e.g., Bypass_Validation__c, By Default: Unchecked (You can hide this field from page pageLout too)
B] Validation Rule
AND( Rating = "Hot", NOT(Bypass_Validation__c) )

This means: Validation rule triggers only if Bypass_Validation__c is NOT checked.

C] While doing Data Loader / Workbench upload, set Bypass_Validation__c = TRUE for records you want to bypass validation.

Result:
Manual insert/update --> FALSE (unchecked) --> Validation rule triggers
Data Loader insert/update --> TRUE (checked) --> Validation rule bypassed

7. Prevent Contact's Blank Email Id.

Ans: ISBLANK(Email)

8. Prevent special symbols and number in the Contact FirstName.

Ans: As it is Pattern Matching, so use REGEX (Regular Expression)
NOT( REGEX(FirstName, "^[A-Za-z ]+$") )

9. Prevent special symbols and number in the Contact FirstName and LastName.

Ans: NOT(REGEX(FirstName, "^[A-Za-z ]+$")) || NOT(REGEX(LastName, "^[A-Za-z ]+$"))

10. Prevent Contact, if age is less than 18.

Ans: (TODAY() - Birthdate) / 365 < 18

11. Prevent Account if Rating is Hot and Type is Prospect.

Ans: AND( Rating = "Hot", Type = "Prospect" )

12. Prevent Account if Rating is Hot or Warm and Type is Prospect or Other.

Ans: AND( OR(Rating = "Hot", Rating = "Warm"), OR(Type = "Prospect", Type = "Other") )

Prevent Invalid Pan Card Number.

Ans: NOT( REGEX(PAN_Number__c, "^[A-Za-z]{5}[0-9]{4}[A-Za-z]$") )

14. Don't allow small letters in the Pan Card.

Ans: NOT( REGEX(PAN_Number__c, "^[A-Z]{5}[0-9]{4}[A-Z]$") )

15. Contact Email Id should be mandatory for 'Customer Care' profile only. Not for other profiles.

Ans: AND( $Profile.Name = "Customer Care", ISBLANK(Email) )

16. Contact Email Id should be mandatory for 'Ganesh Padole' user only. Not for other users.

Ans: AND( $User.Name = "Ganesh Padole", ISBLANK(Email) )

Another Solution

AND( $User.Id = "005xxxxxxxxxxxxxxx", /* Replace with Ganesh Padole's UserId */ ISBLANK(Email) )

17. How do you make a field mandatory only for certain Profiles or Roles?

Ans: Use $Profile.Name or $UserRole.Name in the Validation Rule.

18. How to conditionally require a field based on another field’s value? Example: Email mandatory only if Lead Source = 'Web'.

Ans: AND( ISPICKVAL(LeadSource, "Web"), ISBLANK(Email) )

19. How to prevent special characters or numbers in name fields?/h4>

Ans: Using REGEX

20. How do you enforce proper formatting for IDs like PAN, GSTIN, or Phone Number?

Ans: Regex validation with pattern matching.