How to put music on my iphone without erasing everything?

Normally I use ITunes on my desktop just fine however i also have a laptop that i would like to be able to use as well but when i try putting music on the phone through the iTunes on my laptop it won't let me unless i erase and sync everything on the phone. How do i get around this?

I want to add a different processor to my iPhone 4

So I wanted to replace the A4 chip with the fastest most powerful processor on the planet. The intel i7 3960x. It's costs 1K and runs at lightning speeds but my iPhone will be able to handle it. It's an iPhone right. I wanted to add 16 GB of RAM. Pretty much making my iPhone the fastest iPhone out there. But I want to see a video of how it's done.

How to post a gif to tumblr from an iPhone?

Well I don't have a computer right at this moment because I'm visiting my dad and I just have my iPhone for now. So I find gifs all the time that I LOVE on other websites and I want to post them again on tumblr. Well whenever I do post them, they just show up as pictures which really confuses me because I have no idea how people post them. So yeah. Oh and one more question, and if someone can answer this, ill give them 10 pts. So when I hold down on a gif on TUMBLR to save it, it goes to my gallery and when I send it to someone, it doesn't do anything. It's just a picture. So yeah. I'm trying to work tumblr off my phone and obviously it's not working out. Ugh someone help please!

How to restore an iphone if you forget the passcode?

Tunes keeps telling me that it can't connect to the iPhone because "the iPhone is locked with a pass-code" and apparently I have to connect it to the iTunes to be able to restore it BUT I DON'T *** KNOW THE PASSWORD! What do I do?

Added (1). But the computer can't detect it!

My Iphone 3 won't accept my password

I switched Iphones with my dad, I switched the sim card correctly and everything. When I go to the app store down at the bottom it has the correct apple id info. But when i go and try to update an exsisting app it ask for the password to my dads apple id. I've gone into settings and it has my correct apple id. What do i do!