ZTE Open Series

Graphics Adapter: Qualcomm Adreno 200, Qualcomm Adreno 302
Display: 3.50 inch, 4.00 inch
Weight: 0.1kg, 0.125kg
Price: 100, 200 euro
Average of 5 scores (from 8 reviews)
ZTE Open
Specifications

Processor: Qualcomm Snapdragon S1 MSM7225A
Graphics Adapter: Qualcomm Adreno 200
Display: 3.50 inch, , 480 x 320 pixels
Weight: 0.1kg
Price: 200 euro
Links: ZTE homepage Open (Model)
Pricecompare
Reviews
Source: Engadget

We should reiterate what we said earlier in the review: the ZTE Open is partly intended as a developer phone. For those customers, it does the job well. You don't need a quad-core processor or a 1080p display to demonstrate that your HTML5 app runs properly.
Single Review, online available, Long, Date: 10/03/2013
ZTE Open C
The ZTE Open C packs a combination of budget hardware and the new OS from Firefox. Being an entry-level device, it is definitely cheap to own, but it might not be everyone's cup of tea. Specifications are as basic as it gets with a 1.2 GHz Cortex-A7 dual-core processor, Adreno 302 GPU, 512 MB RAM and 4GB internal memory.
There is an option to add storage space with a MicroSD card up to 32 GB. The display is a 4 inches TFT capacitive touchscreen which does a decent job. There is only a rear 3.15 MP camera, which is less than impressive. Other features include FM radio, GPS with A-GPS technology and WiFi capability; all being pretty much expected to be included in modern budget smartphones.
The operating system is still in development and has straight forward features, but there is currently a lack of applications. The device itself feels sluggish and the exterior simply looks cheap.
The 1400 Li-ion battery is more than enough to sustain a basic smartphone. Overall, there is much to consider before purchasing the ZTE Open C and many users will skip the option when they try one out.
Specifications

Processor: Qualcomm Snapdragon 200 200 8210
Graphics Adapter: Qualcomm Adreno 302
Display: 4.00 inch, 5:3, 800 x 480 pixels
Weight: 0.125kg
Price: 100 euro
Links: ZTE homepage Open C (Model)
Pricecompare
Average Score:
Reviews
Source: Expert Reviews

The ZTE Open C is very cheap, but its terrible battery life, token camera, poor screen and limited selection of apps and services place it very much at the bottom of the bargain bin. It's also only available SIM-free as an eBay exclusive from ZTE's eBay store, making it more difficult to get help if something goes wrong. If you can spend a little more, the £90 Motorola Moto E is a vastly superior phone that's much better value.
Single Review, online available, Very Short, Date: 10/07/2014
Rating: Total score: 40%
Source: Trusted Reviews

Firefox OS’s aim of bringing smartphones to emerging markets is interesting. But a £70 Firefox OS phone like the ZTE Open C doesn’t make a great deal of sense to most UK buyers when the system is severely compromised, and Android alternatives don’t cost much more.
Single Review, online available, Short, Date: 06/28/2014
Rating: Total score: 50% price: 70% performance: 60% features: 60% display: 60% mobility: 50% workmanship: 50%
Source: Techradar

The ZTE Open C is very cheap and as a first smartphone it could certainly do a job. It represents a definite step up from the realm of feature phones. The trouble is you can get a number of smartphones that are a lot better for just a smidgen more cash. The Moto E and the Lumia 520 are superior in terms of specs, performance, and platform and they're not a lot more.
Single Review, online available, Very Long, Date: 06/18/2014
Rating: Total score: 50% price: 80% performance: 40% features: 40% workmanship: 60%
Source: Tech Advisor

The ZTE Open C smartphone costs only £60, and that’s the unlocked price so you can put a SIM from any operator into it. It runs the open source Firefox OS, and is aimed mainly at emerging markets such as China and India. However, you can buy it in the UK from ZTE’s ebay shop.
video review
Single Review, online available, Very Short, Date: 06/17/2014
Source: Tech Advisor

The Open C is an unlocked smartphone which costs very little. Although it’s better than the original ZTE Open, performance isn’t great and the operating system makes the 4in screen appear to have even fewer pixels than it does. If you’re on a really tight budget, you’d be better off going for a pay-as-you-go smartphone such as the Lumia 520, which will cost you just £75 locked to a mobile operator such as T-Mobile or Vodafone. If you’d prefer Android, then look to the Moto E.
Single Review, online available, Very Short, Date: 06/13/2014
Rating: Total score: 50% price: 60% performance: 40% features: 50% workmanship: 40%
Source: PC Mag

There are very few unlocked smartphones available for under $100 in the U.S. Note that I'm saying unlocked; it's perfectly possible to get a prepaid, but carrier-locked Android or Windows Phone for under $100. For unlocked phones, though, your best options are lower-end devices from BLU or gray-market Samsung or LG devices. That's why we're rating the Open C as high as we are: It's quite a feat for a sub-$100 device.
Single Review, online available, Very Short, Date: 06/13/2014
Rating: Total score: 60%
Foreign Reviews
Source: c't - Heft 05/2015

Review Type Unknown, online available, Length Unknown, Date: 02/16/2015
Comment
ZTE:
ZTE is short for Zhong Xing Telecommunication Equipment Company Limited, which was founded in China in 1985 and is partly state-owned. ZTE's core business is wireless, optical transmission, data transmission equipment, telecommunications software and cell phones, USB sticks, routers and tablets.
These graphics cards are not suited for Windows 3D games. Office and Internet surfing however is possible.
Qualcomm Adreno 200: Integrated GPU in the Snapdragon S1 SoCs and based on the AMD Z430. Later called Adreno 200 with higher clock speeds.
Qualcomm Adreno 302: Integrated graphics card in some Snapdragon 200 SoCs with 6 shaders clocked at 400 MHz.
» Further information can be found in our Comparison of Mobile Graphics Cards and the corresponding Benchmark List.
Qualcomm Snapdragon:
S1 MSM7225A: Entry level Soc with one Cortex-A5 processor core (clocked at 600, 800 or 1000 MHz depending to the device) and a Adreno 200 GPU.
Qualcomm Snapdragon 200:
200 8210:
ARM Cortex-A7 dual core with a max of 1.2 GHz clock rate
» Further information can be found in our Comparison of Mobile Processsors.
3.50:
This display is tiny. You will probably see very little on the screen and be able to use mini-resolutions.
» To find out how fine a display is, see our DPI List.
No weight comment found (one expected)!
50%: This rating is bad and very rare. There are only a few models that are rated so poorly. If the source is reputable, then a purchase is probably not advisable.
» Further information can be found in our Notebook Purchase Guide.