Why can I only turn on iMessage when Wi-Fi is on (iPhone)?

I have an iPhone 5s, and when I'm out of the house I turn iMessage off to send photos so it doesn't cost me data. When I try to turn it back on (Cellular, no Wi-Fi) it says I have to turn on Cellular or Wi-Fi (Cellular is already on) how can I fix this?

Are Factory Unlocked iphones any good? Will there be problems?

I'm thinking about getting some iphones for my mother and her boyfriend for Christmas. (I know, its way early to be thinking about any presents, but i'm just browsing around). Since i do not know exactly what carrier they are with i'm just looking around at Factory Unlocked iphones, say i do get the phones, They're shouldn't be any problems when they go to use the phone with their carrier will they?
Also, (Just wondering) How will the i know the seller is telling the truth that the phone is unlocked, if i do get the phones, will there be some way i will be able to tell if the phone is factory unlocked?

I accidentally locked my iPhone 4s?

So, I accidentally entered my SIM code wrong three times in a row, now I need the PUK code. The phone was given to be second hand by a friend. I use it as a iPod touch type thing and it has no service. How do I get the PUK code?

My iphone isn't receiving texts from an android?

My iphone 5 randomly hasn't been receiving regular texts, pictures or videos from someone with an android. I get most of them but for some reason even though they say they've been sent, i'm not receiving them

Honest thoughts about my photography?

I used my iPhone for photography and want an honest opinon. Also, would you suggest I buy an actual camera and try to do something with my skill (If I have any?)