As an iPhone user, do i need to install jailbreak on my mobile in order to get mobile applications free download?

Yes and No. You can download free apps from App store without jailbreaking your iPhone. There are several apps that are totally free like skype , viber , instagram and several games and other tools. Jailbreaking lets you install a substitute app store where apps are free and you can do some customisations in the OS but jailbreaking is not recommended unless you are some sort of developer or someone who loves an open source Operating System. Do not jailbreak unless you really want to. 

It's the endless argument, but Steve Jobs created iPhone as closed system. It means any jailbreak intervention carries in  the risk to make the iPhone system misbalanced and may cause unwanted bags come up, e.g. battery rapid discharging, memory effectiveness usage down, etc. In many cases warranty support could be declined if any intervention would be found. Therefore if user would like to expand the horizons and ready to take that risk the selection of jailbrake method should be very much careful. 

I do not know, I'm from users of the Android system.

I really don't know , I'm an Android User.

There's this third-party tool for iOS that lets you download many applications for free on your iphone (also in the PC). I personally use AppCola and i-Funbox. You can watch youtube tutorials how to download apps for free on your iphone without jailbreaking your phone.

Only Free application can be downloaded without jail break but for any chargeable applications you will need jailbreak to download it for free, however this will put you in risk of system failure or damage, moreover you will lose your warranty if you have one, 

Www.pangu.com go to this site and install this app.and also you can search in YouTube how to jailbreak

Thank You for the invitation .. I would agree with answers.. Variety of correct info and opinions ... Nothing to add !

Free apps can be downloaded from APP store without jail breaking like skype, whatsapp etc. Jailbreaking substitutes app store for customization, and need some technical sense.

There are so many free Apps @ App-store too, so it is not a must to install free apps, but it is a need to install apps not verified and/or authorized according to apple's regulations

That will be a wrong choice ,may be  you will be happy for the first 2 months as you will get free apps and free games , later on you will know your mistake ... as jailbreak : its made to break your phone security system as well .. Please note no body giving things for free nowadays !!