Dash js (algorithm related to controlling video quality level)

[Zayed766]

I have two questions that i need an answer for my graduation project.

The first question is that is there a rule or way that i can limit the video quality level fluctuations? And how can i edit it in my html code?

the second question is that is there a way that i can control video quality level in a way that i start with very low quality and then improve it in ascending order To eventually reach the higher quality level?