Question 1

Could someone please tell me whether this is only for 48V cameras as we have 12V. Thanks.

Accepted Answer

The PoE standard is 48V and all PoE switches (or PoE injectors/power supplies) (except some older models made before it was standardised), and the MokerLink 8 Port Gigabit PoE Switch  is certainly a fine example of a 48V  PoE switch.
The important thing to remember is that even if your camera takes 12V from a directly-connected power supply, if (and ONLY IF) it is also PoE compatible, then it will work fine with power over ethernet at the standard 48V. (That 48V  is then converted down, inside the camera, to the voltage it needs, but over longer and thinner cables, as the ethernet cables tend to be, it is far more efficient and easier to send higher voltage and lower intensity (mA) of current, to provide the power needed, then to send lower voltage and higher intensity mA)
If your camera is not PoE compatible, then the switch will identify that and will not send power down the Ethernet cable and you will need to use a 12V power supply

Question 2

What does the "extend" switch actually do, no mention of it in the manual?

Accepted Answer

"Context is King" and most words don't mean much in isolation. That applies to "extend" in your question. If you would like to , perhaps, rephrase the question, including the whole phrase with "extend" in it, then, more people would be in a better position to give aproper, correct reply. I had a quick look at the item's description, on the Amazon page andI could not find the "extend". 
I hope this helps

Question 3

Can i connect one uplink port to my nvr and the other to my broadband router to allow me access to my home cctv images on my ipad/mobile phone?

Accepted Answer

Uplink ports are special ports, normally used for up-linking "up the tree" or for stacking multiple switches together and if I had a choice, I would not use them for anything else.
Having said that, I will point out that speciality /technical literature says that "There are multiple other uses for uplink ports, and, in some instances, you can even use an uplink port in place of a normal port" so I believe that you should be able to use the configuration you mentioned, but unless  you are tight for downstream ports for your cameras and other devices, I would connect it like this:
Connect just one uplink port to the broadband router (which, from how you formulated the question, I guess also has the access point, probably built in or connected to it)
Connect a "normal" /downstream port  to the NVR and other downstream ports to the cameras.  That configuration will work.
I hope this helps

Question 4

Are the 'hangers' included suitable for rackmounting?

Accepted Answer

No

Product dimensions	20L x 11.8W x 4.4H centimetres
Voltage	24 Volts
Case material type	Metal
Interface type	RJ45, SFP, PoE+
Data transfer rate	1000 Megabits Per Second
Manufacturer	MokerLink
UPC	786118199835
Item model number	11 Gigabit PoE
Number of Ethernet Ports	10
Wattage	120 watts
Power Source	AC
Are Batteries Included	No
Item Weight	990 g
Guaranteed software updates until	unknown

11-Port Gigabit PoE Switch

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