Q: I have iPad 1 it is supported iOS 5.1.1 maximum. I could not download apps like Facebook or olx and much more have required iOS 6 or letter. What I do to download apps from apple store.

Unfortunately there is nothing you can do other than updating your iPad.

Pete

Actually you need a later model of the iPad to run all current Apps.

There are still some Apps running on earlier iOS and facebook can also be used with Safari.

Just check the web, maybe you will find some Apps that you like and wich are running on iOS 5.1.

Charly

The article below may help.

https://sites.google.com/site/appleclubfhs/support/advice-and-articles/app-store -downloading-older-versions-of-apps-ios

You can in fact install older versions of apps that are compatible with your iOS as long as the older versions are still available. It is up to the developer to make the older versions available.

Make sure that you read the articles that stedman1 referenced above. It is more detailed than how Apple explains it here.

Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support