Upgrade iphone by switching sims?

I have a company iPhone 4s from sprint. I also have a personal cell phone but am tired of having to pay for it and carry two phones. I want to upgrade my work phone but my company doesn't want to upgrade me. If I buy a 5s or a 6 myself is it possible to just swap SIM cards into it? Would my company notice anything on the bill if I did this without them knowing?

What's a good free music download app for IPhone?

I was wondering if there are any good apps for iPhone that let you download whatever songs you want for free. Itube was awesome but now it won't let you download the songs and you need Wi-Fi to listen to them. Is there an app that lets you download YouTube videos for free and watch them without Wi-Fi or Internet?

How to make an iPhone app, based on html/javascript?

I want to make an application with html/javascript, for the iPhone. However, I'm not looking to get it on the app store. I want it to be dowloadable from a website, kind of like OpenAppMkt. They would visit the page, then click add to home screen (shortcut), then it will be the app. Does anyone know how to do this?