Dear Nirav,
OLT is meant for professionals so as to pursue on-job training on the module they are working.
ILT is for those who are on the other side that is desiring full time training.
Certification Exam doesn't need benifits of ILT or real time experience or even OLT if you are already into certification programme.
I myself have undergone for OLT.
Certification exam can be cracked by anybody who have studied thoroughly the SAP Certification Course books. Ofcourse prepare a demo test in many online sites also trying certification
does help.
To gain some real time scenarios local institutes are sometimes good as Professional Individuals are being hired to train the aspirants. Also you can have ghost installation or Server Access for Demo IDES and you can practice.
Hope the info helps You, and ALL THE BEST for your certification..
Best Regards,
Aparajit 