One design for computer and mobile

Question

Hi, i'm kind of a nubie to Muse CC, but love what i've seen so far...so much so that i also purchased a one-year subscription to muse-themes.com, in order to download a theme that would give me a head-start with a new portfolio site i have to do for myself.
Just to explain why i'm only a noob to Muse CC, but not to web-design as a whole:
I have used the Creative Suites for many, many years, and before that used Photoshop and Dreamweaver to "hand program" my sites, so i'm an HTML veteran of 15 years...no experience with Javascript or anything like that, but i've done my own sites from scratch since the old Netscape days.
Back to my issue/question:
After modifying the template i downloaded from muse-themes.com and doing a first few hours of customization on it (some text, headers and images) and using business catalyst to preview what i've done, and quite liked it for a first start, but when checking the design on my iPad, i discovered with disappointment that not only did it not show *any* of my customizations (only the original, generic theme design and content), but even then, menu items had weird glitches, and the long scrolling content of the computer version didn't appear after the first couple of page-heights.
Let's forget about the glitches for moment...my main question is:
If a theme has been designed with Desktop, Tabel and Phone versions in mind, will i have to maintain content and all changes *separately* for all 3 platforms?! is there a way to "sync" changes between platforms...in other words, since Computer and Tablet versions should pretty much be exactly the same, can i have Muse automatically interpret what i do for the Computer version *also* for the Tablet version? i do understand that the Phone version should get special attention, but even then, shouldn't text and header changes "trickle down" through all versions of the site?
Am i doing something wrong here, or is building 3 separate versions independently really what i am expected to do?
I keep seeing many references to "responsive UI designs"...is this why people work on one responsive design, rather than on 3 separate versions, or are those issues not really related?
Excuse my naive questions, but i have a difficult time believing that Muse CC, and/or a custom theme, purchased from a reputable 3rd party company (such as muse-themes), would require me to maintain 3 websites for 3 device platforms, with no "communication" between the 3 during the design process...there must be a way to "sync" my changes/updates, or is this really so?
Just to illustrate what i am talking about, here is the first revision of the theme i purchased:
http://kruegervp.businesscatalyst.com/index.html#top

Answer 1

Hope I can help here .....
The first issue is most likely a Business Catalyst caching issue that pops up occasionally. Or it could be that the original template had a Tablet view done and that is what you are seeing instead of the desktop view.
Yes, you will need to maintain content seperately on the different views. This is actually a good thing in my opinion as you likely won't want all the same content on all three.  As for the responsive sites, while yes you do have to only update once it also can take a much longer time to develop to get consistant results. With the so many different browser widths now it is getting more and more difficult to display the site consistantly and properly.
So while one may be more to update it is much less to develop and the other is much more to develop but less to maintain. It works out in the end.