You spent your time collecting and organizing questions, what is left is to define a question paper, assign it to candidates and evaluate.
Zoho Challenge offers a lot of flexibility here. You can control when a test can be started (including open for ever), how long it will last (you can make it last indefinitely too). Zoho Challenge has built in controls that automatically terminate an in-progress test after the cut-off - of course with sufficient visual warning to the user.
Random Questions or Ordering
You can create a test to deliver randomly picked questions. You can also randomize the order in which even fixed questions appear in the test. You can also shuffle the order in which choices are presented to the user. Introduce Chaos to gain order and effectiveness.
Section By Section Tests
A question paper in Zoho Challenge can comprise of several sections. Each section can have several questions. You can have section specific instructions and also setup to advance the question paper one section at a time.
Not all questions can be evaluated automatically. Some questions have creativity involved and are best answered in essays and paragraphs. Others might not always have a fixed set of choices. A creative student can choose an "other" choice and justify his/her stand. In such situations, manual evaluation can be the best recourse. Zoho Challenge lets you partition this task between multiple evaluators while sharing a common answer key to minimize subjectivity.
You can setup tests so that wrong attempts (typically caused by guesswork) can be penalized with a negative mark. This negative mark can be a percentage of the max score or can be a fixed negative mark. Setting up a real competitive exam or just preparing for one has never been easier.