This watch has a case diameter of 30mm and a case thickness of 9mm.
#4 Can the upper 2 links having crystal be replaced with normal links?
The links closest to the face of the watch are permanent links and cannot be removed.
#5 Are the watches a standard size because i dont want a big watch for my small wrist.
They are not all a standard size. The case diameter will give you the size and you can usually find a sizing chart online to see how that would look when on. This particular watch is small, not oversized at all.