1) If two users A and B under same profile and Role. How can I restrict records of A to B and Vise versa?
Ans: In profile set View all data and modify all date permission is 'false' and Owd Should be Private then we can restrict data.

Difference between Data Management and Data Loader?  

Data ManagementData Loader
We can insert 50000 records per Transaction.We can insert 5 million records per Transaction.
Duplicate records it cannot allow.    We can insert Duplicate Records.
We can perform operations in any custom object and four standard objects Account, Contact, Lead, Solution, Campaign member.We can perform operations in any custom and standard objects.
It can perform operations insert, update, upsert (insert + update).  It can perform operations insert, update, upsert (insert + update), delete, Export, Export all.
It allows only CSV files.It allows CSV all database files.

2. Difference between lookup and master details?

LookupMaster
we can create a max 40 lookup relations (including 2 master details) per objectWe can create max 2 master details relationships per object.
This relation is supporting standard and custom objectsMaster details is supporting only custom objects.
We can create a lookup for empty objects (without records and also with records)We can create a master-detail relationship only in the empty object because the parent field value is mandatory. Note: if any object contains any record first create a lookup relation then fill all parent field values and change relationship type lookup to master-detail.
In lookup relation, parent and child contain their own owner.Parent and child are controlled by a parent it means parent object only contains ownership on child records.
It cannot support inheritance in OWD and sharing rules. It supports inheritance in OWD and sharing rules.
It cannot support the roll-up summary.It supports the roll-up summary.
In lookup parent record is deleted, the child field value is deleted. But not record.In master-detail parent record is deleted, Associated child record also deleted because parent field value is mandatory. Note: This rule is applicable to up to 200 Childs. If any parent is associated with 200 or more then we cannot delete the parent record
In lookup relation parent field value optional.In lookup relation parent field value mandatory.

3. Difference Between SOQL and SOSL?

SOQLSOSL
SOQL stands for Salesforce Object query language.SOSL stands for Salesforce Object search language.
Need to write different SOQL against diff objects.works on multiple objects at the same time.
It Returns a list of Records. It returns a list of Subjects.
Can be used in apex classes and triggers.Cannot be used in triggers, can be used in apex classes anonymous block.

4. Difference between Roles and Profiles

RolesProfiles
Role hierarchy doesn’t do any of these things.Profile manages the Salesforce.com License, Object permissions, Field permissions, User permissions, Tab settings, App settings, Apex class access, Visual force page access, Page layouts, Record Types, Login hours & Login IP ranges, etc
Optional for User creation.Mandatory for User creation.
Maintain Record level access.Maintain object-level access.
The role is not  Mandatory.The profile is Mandatory.
The role helps in opening the records to the users above the Role hierarchy.The profile helps to put restrictions on the Object.

5. Difference between Workflow and Approval Process?  

WorkflowApproval Process
They are activated when a record is saved. An approval process is triggered by explicitly clicking the “Submit for Approval” button.
Workflow consists of a single step and the single-action  Approval process consists of multiple steps. Also, a different action is taken based on whether the record is approved or rejected.     The approval process consists of multiple steps. Also, a different action is taken based upon whether the record is approved or rejected.
The workflow consists of a single step and single action.In approvals, some attributes cannot be modified. Processes must be deactivated before approvals delete.

6. . Difference Between Trigger. New and Trigger.NewMap in Apex?

Trigger. NewTrigger.NewMap
Returns a list of the new versions of the sObject records.Returns a map of IDs to the new versions of the sObject records.
Note that this sObject list is only available in insert and update triggers, and the records can only be modified before triggers.Note that this map is only available in before update, after insert, and after update triggers.
Trigger.newMap doesn't work for before insert while.Trigger.New works fine for holding all Ids of records while inserting.
Trigger.new returns a list, which are ordered.Trigger.newMap returns a map – which is unordered.