How to install apps on older iphone 3gs(ios 4.1)?

You'll need to download them with iTunes. Then when you go to the App Store on your iPhone, you'll be offered a legacy version of the app if the developer offers it. There may not be very many of them left.

That's fine; you can download them into iTunes, then do as I said above. Go to the store on your phone and try to get the legacy version of the app with your phone.

I already did. You may want to think about getting a newer phone if you're having this many problems. The phone you have is now six years old and very outdated. It's time to upgrade.

kstbespoo wrote:

yeah thatstrue but can u help me with skype?

Skype is not an Apple product so contact Skype support.

You failed to mention that you have a jailbroken phone. You are on your own as Apple does not support jailbroken devices. Goodbye.