Will this trial version of Avast antivirus stop all the threats?
Yes, why wont it? And avast is free.
It indeed does the only difference between the free version and paid version is that you will not have some additional features such as software updater in free version and the anti virus is completely operational.
Yes, if it is the latest version of the program, it should stop all the treats. Also, you need to know that if you register the product using the Register option, you will receive a free license available for one year. Contact the official developers for further details.