You will probably be able to do the string formatting as outlined in Solution 1, but in my experience, your basic approach is bound to cause major problems later on.
Say you get to the point where your integer has the value 111024. Is that supposed to be interpreted as 11.1.024 or 1.11.024? There are other nasty things that you probably are not considering right now - believe me, been there, done that.
I suggest you drop the integer and instead use the class System.Version
]. Take a look at it and notice all the ways you can set the values.
I doubt the built-in ToString() will create the format you want, but then you are free to do you own string formatting, using the properties Major, Minor, etc.