Does the iphone 3gs still work?

Forgive my ignorance but i'm not used to cell phones.
My friend is trying to sell me an iphone 3gs for $50, he said there's nothing wrong with it except it has a cracked screen.
a couple of months ago his brother bought an iphone(not sure which one) but it wasn't able to be used as a cell phone because it was too old.

So my question is, if I bought this iphone could I activate it(Tmobile) and be able to use it like any normal cell phone?

What is a good bluetooth transmitter for my bluetooth enabled truck?

I have a bluetooth enabled truck, so I can make and receive phone calls through my iPhone 5, but I'm looking for a transmitter that I can plug into my iPhone 5 and have it work through bluetooth to send the music to my sound system. I don't want one that is just an FM transmitter that would plug into my phone and work through a radio station. I want one that will plug into my iPhone 5's charging port or headphone jack and send the music via bluetooth to my sound system. Is there a product out there that is like that, or am I just stuck with buying a FM transmitter? I have a 2009 Toyota Tacoma, that does have a AUX port, but it has broken twice on me and costs $200 to fix, and I really don't want to spend another $200 for a new one just to have it break again. Any suggestions, and links would be greatly appreciated.

Added (1). It does have Bluetooth built in, but with my 2009 Toyota Tacoma it only works with making and receiving phone calls, it doesn't work with sending music via bluetooth.

Iphone and samsung galaxy s4

Hi so I got a samsung galaxy s4 yesterday because my iPhone was slow but now whenever someone with imessage messages me it goes to my iphone even though it has no simcard in it. How do I change this because I can't receive messages on my Samsung galaxy S4 from people with an iPhone? ♡

Why can't I import the photos from my IPhone 5 to my Macbook Pro?

So I have a little over 1000 picture on my IPhone 5 and i want to get them to go onto my Macbook Pro laptop. I know this probably sounds stupid, but I just can't seem to figure it out! I've researched a lot of stuff and even went onto the apple website! I asked a few of my friends who have PC laptops and they said that a little pop-up came out in the corner of their screen asking to sync their photos. Well of course my doesn't have a pop-up.