Second conditional in English- Correct usage?

I am confused about the second conditional in English. I have just had a look at these sites.

http://www.usingenglish.com/articles/english-conditionals-second-conditional.html
http://www.usingenglish.com/glossary/2nd-conditional.html

and

http://www.englishpage.com/conditional/pastconditional.html

On the first two sites it’s given that this conditional rule is applied when the situations
are unreal/imaginary, but on the third site it’s totally different one.

Can you tell me the correct use of second conditional in English?

These are some expamples:

If you had a good time with ABC hotel, ring the bell.

If interested, apply for this job.

Forgive me If was wrong.

Can anyone clear my confusion?. What do above sentences mean? Please explain it to me.

Helpful responses would be appreciated. :)