sentence A: Many YouTube videos will play using HTML5 in supported browsers.
sentence B: You can request that the HTML5 player be used if your browser doesn't use it by default.
Hello. The above passage is from a youtube page. I made the words bold which I am about to ask about.
I have 3 question about that passage.
Question 1) In the sentence A, doesn't the part "using~" mean a method or a way of playing? Then, why is "by using" not used instead of "using" there?
Question 2) In the sentence B, why is "be" used instead of just "is"? Is there any word omitted before "be", for example, "should" or "may"? I wish to get an explanation about this.
Question 3) In the sentence B, why is "by" used before "default"? I think "as" or "for" are much more appropriate to it. Or all of them are usuable here?
P.S. I always thank you so much for your sincere, brilliant helps. Even a very short, simple explanation is very helpful to me.