How to stop your iPhone from turning off by itself?

I'm trying to watch a YouTube video and it keeps on turning off and the youtube video turns off too which is normal to regular phones. But, I want to set it up in my setting as to where it never turns off unless I switch it off myself.

Can i add on another line to my tmobile plan if?

Ok so I want to buy my son an iPhone 5s on Saturday December 6 2014. But my phone bill is the next DAY December 7 2014 Sunday. I don't want to add on the line and get charged for it the next day on my bill. So I wanted to know if I can go to the store on the 6th and pay my phone bill early and then add on the line. So that way the bill won't go up right then because I will have already payed the bill. So the bill will go up for the next time. Is this possible. Can I pay my bill before hand and then add on a line to my plan? BTW the phone is $0 down so I won't have to pay anything in the stores.

Can wireless devices connect to bridge router?

I have a D-link router(with modem) which I use to connect to the internet. But the range of the Wi-Fi is not very good. I have an old router and I want to use this to extend my range. If I change it into an access point I have to connect both the routers using a very long ethernet cable(or powerline adapters). But what if I bridge the router. Now I know that wired devices can access the internet by connecting to the bridge router which is in communication with the main router. I want to know if wireless devices(such as an iphone) can connect to the bridge router and access the internet. If this is difficult to understand look at the following and tell if it is possible:

Main router <wireless> Bridge router <wireless>laptop or iphone.

My computers pictures are stuck on my Iphone?

Somehow, when I was syncing my pictures from my iPhone to my computer, all of my computer photos copied onto my phone, and now I can't get them off as there's no option to delete! Its taking up loads of my storage so I need to get them off, any help?!

Did Apple fix the iPhone to other devices' iMessage problem?

I read that switching from Apple to Samsung there were problems such as the Samsung phone trying to send iMessages to iPhone users, making it unable to text with anybody that uses the iPhone. I recently went from the iPhone 4s to the Galaxy s5 and I don't see any problems with messaging but I'm worried that there are other things such as problems with Cloud or iTunes, etc. Did Apple fix all of those problems, or do I just not know about them? Because i don't know, I feel like there are no problems so far.