Can I use different apple id on y iPhone?

I got a new iphone and sync apps from an old one. I use one apple id for both ( with this apple id I download and buy some apps ) now can I use a different apple id on my new iphone?
can I use apps (that I bought or downloaded with my old apple id )with a new apple id without any problem?

Can the Tumblr virus affect iPhones?

If you're a tumblr user, you probably have heard of a virus going around that hijacks your computer and takes you to a FBI site that forces you to pay to be released (which if you've paid, it doesn't release you at all). So, can you get the virus if you use the tumblr app on iPhones?

I was very curious about black market websites and found myself on some weird stuff?

I downloaded onion browser on my iPhone and found some weird stuff there via the links they provided. Stuff like hard drugs, guns and hit men saying they were willing to kill. I'm very worried now because I was searching for this stuff and I know iOS will still be able to trace this stuff up.
I haven't bought anything. Does anybody have any advice on what I should do?

Can I keep my iPhone and number if I switch from AT&T to T-Mobile?

I have an iPhone 4S running iOS 6.0 and I bought it around May or June of 2012. I have had the carrier AT&T the whole time I have had this phone, but my parents would like to switch our service to T-Mobile. Everyone in my household have upgraded to newer phones, but I have kept this phone the whole time.

I heard T-Mobile makes you buy a new phone if you switch to them. Is that correct and how would it apply in this situation?

Am I able to keep the same phone number?

Am I required to use an iTunes backup, and can I do that without having to upgrade to iOS 7?

How to stop old messages and email appearing in spotlight on my iPhone?

I have and iPhone 3GS, so I'm running IOS 6, and whenever I go to spotlight and press any letter old messages and emails that I deleted AGES ago keep appearing, then when I click them it just opens the email app or the messages app, I know you can turn it off but I'm a bit annoyed incase they are taking up space, I know it won't be taking up a lot but over time it will get worse, I also know you can turn it off but I want to stop them appearing at all, so is there anyway I can delete them for good or it turning them off the only way?