Sequece of Meditation and Side Effects

https://www.youtube.com/watch?v=kkKOyV_pJ74 Refer to the image and video above, Venerable Guan Cheng explains that meditation should be practiced after proper moral virtue/Sila been achieved for the monks. **Question 1:** Does side effects occur due to basic or minimum of Buddhism Precepts or Sila (requirement) not been achieved yet? Most Common side effects could be hallucination, feeling dizziness or more example below Meditation side effects Unpleasant side effects of meditation **Question 2:** As a lay Buddhist, is it a right practice if the sequence is wrong or Sila/Precepts and Meditation being practiced together? If no, then at what stage of requirements? Well, i know at least not after being drunk and go meditate. https://en.wikipedia.org/wiki/Five_precepts **Post Note**: In the Youtube video above at 57:00, Venerable Guan Cheng explains that those monk only focusing on Moral Virtue before start meditation for the first five years. I had recently re-verify with another Bhante and he mentioned also must follow the sequence.