Stunt Driving Witness Trial Appearance Help

Hey, guys, this is my first time on the forum and some help/clarification would be really nice. Okay, so what happened was that my friend was driving way to fast with me and another person in the car. He got pulled over by the York Regional Police and was charged with stunt driving and excessive speed. (127 km/h in a 40). At the time of the stop, he received one ticket for 77 km/h in a 40. However, the officer came back 2 mins later demanding the first ticket back and my friends license back as he was apparently clocked by another officer going 127 km/h. The officer that clocked him at 127 was part of a high school physics demonstration and it was actually a student in possession of the radar gun at the time that he was clocked, not the officer. His hearing was on Friday May 25th, 2018. The officer showed up and said that he tried to run from him. Which is 100% false and the officer said that he has no dash cam proof or proof in general of him running. So my questions are that:

1. Can an officer take back a ticket after it is already written with no proof regarding the change in speed? If not will the 127 be dropped?

2. Because the student was holding the gun, does it make that evidence inadmissible?

3. As a witness (because I was in the car) do I have to testify? I am really not comfortable testifying in court.

1. Yes a ticket can be cancelled and a new one issued.

2. Not necessarily but it will be something you can address in court.

3. If you are subpoena'd, you are required to attend or the court case issue a warrant for your arrest.

127 in a 40 (and presumably close to a school if there were students there being shown the equipment) is a very serious matter. Your friend is lucky he didn't get a criminal charge of Dangerous Driving.