In-class pop quizzes (online) and how to moderate them
Given the limitations of the material of the students and at your disposition why do you do a quiz on internet? You can be assured that students talk between themselves. I think that you should simply do the quizz in class with pen and paper to be really fair. 

If you have a large number of students, you could do most of the quizz as multiple choice questions and use a device (scantron?) to correct them automatically. As a complement you could have a few questions with one word answers.