There's a couple of ways to do this. You can remove the battery, put it back on, then start the phone back up as usual. If it still takes you to a password screen, then the only other option (which will essentially be a factory reset, deleting all data) is to hold the volume down, camera, and power buttons at the same time, go into recovery mode, and your phone will start up back to factory settings.
Press and hold the Power, not home button at the same time as the volume down key
Your particular ZTE phone has at least have Android OS 2.1 or newer, and is able to receive calls or SMS in the setup process.
The only way to get a reboost pin for a ZTE phone is to purchase a reboost card at your local retailer.
If you mean how would you take a screenshot on a ZTE Skate, you would just need to hold the Power and Home buttons at the same time. The screen displayed will get captured and will save in your phone's Gallery.
Unfortunately you cannot do so, I there are no compatible flashlight applications without a root. There is a glitch/work around however. To use the flash as a light source open the default camera app take a picture and right when the flash turns on hit the home screen the led should stay on and you can enjoy the light! Just make shure you don't leave it on too long as it does heat up sometimes...? Hope I helped!