Bakod, I would suggest to you to contact the embassy directly so you can get first hand information on requirements and paperwork

their site is

http://www.lebanonembassy-qatar.org/

Contact details

http://www.lebanonembassy-qatar.org/index.php/contact-us

And for visas (and other documents) check the consular services section

http://www.lebanonembassy-qatar.org/index.php/consular-services

http://www.lebanonembassy-qatar.org/index.php/consular-services/visas#To...

Regards!!