Why do I need a by-law to change my windows?

I am interested in installing Double-Glazed windows to block out road noise. But I am SO confused about how this works (Im very new to all this Strata stuff).

Here are my questions, any feedback would be massively appreciated:

1. If Strata agrees to me replacing my windows (at my cost), does this mean I am forever responsible for the windows moving forward? From what I gather I will have to have a By-Law created especially for my Unit? What exactly does that mean?

2. If I sell my Unit in the future, after replacing the windows, will the future owner have to sign a special agreement saying they are responsible for the windows? Will this hurt my chance of a sale?

3. The windows in my building are old, and I know that Strata are actually considering possibly upgrading all of them at some point. If they do go ahead with this, and I have already upgraded my windows, does this mean I will have to remove my windows and have their ones installed?  If that was the case, then I cant imagine why anyone would ever risk paying loads of money to upgrade windows, if they might have to remove them again anyway and then pay for another set chosen by Strata.

Sorry if my questions are amateur-ish. I really am new to all this Strata stuff and it confuses the hell out of me.

Many thanks for any replies,

T.