1. Why there is frequent load failures during extractions? and how they are going to analyse them? 

If these failures are related to Data,, there might be data inconsistency in source system..though you are handling properly in transfer rules. You can monitor these issues in T-code -> RSMO and PSA (failed records).and update .

If you are talking about whole extraction process, there might be issues of work process scheduling and IDoc transfer to target system from source system.   These issues can be re-initiated by canceling that specific data load and ( usually by changing Request color from Yellow - > Red in RSMO).. and restart the extraction.

2. Can anyone explain briefly about 0record modes in ODS? 

ORECORDMODE is SAP Delivered object and will be added to ODS object while activating. Using this ODS will be updated during DELTA loads.. This has three possible values ( X D R)..  D & R is for deleting and removing records and X is for skipping records during delta load.

3. What is reconciliation in bw? What the procedure to do reconciliation? 

Reconcilation is the process of comparing the data after it is transferred to the BW system with the source system. The procedure to do reconcilation is either you can check the data from the SE16 if the data is coming from a particular table only or if the datasource is any std datasource then the data is coming from the many tables in that scenario what I used to do ask the R/3 consultant to report on that particular selections and used to get the data in the excel sheet and then used to reconcile with the data in BW . If you are familiar with the reports of R/3 then you are good to go meaning you need not be dependant on the R/3 consultant ( its better to know which reports to run to check the data ).

4. What is the daily task we do in production support.How many times we will extract the data at what times. 

It depends... Data load timings are in the range of 30 mins to 8 hrs. This time is depends in number of records and kind of transfer rules you have provided.  If transfer rules have some kind of round about transfer rules and updates rules has calculations for customized key figures...   long times are expected..

Usually You need to work on RSMO and see what records are failing.. and update from PSA.

5. What are some of the frequent failures and errors?

As the frequent failures and errors , there is no fixed reason for the load to be fail , if you want it for the interview perspective I would answer it in this way.

a) Loads can be failed due to the invalid characters
b) Can be because of the deadlock in the system
c) Can be becuase of previuos load failure , if the load is dependant on other loads
d) Can be because of erreneous records
e) Can be because of RFC connections

These are some of the reasons for the load failures