When solving a simple assignment problem in Maple 2015.1 the bug occurs:

In Maple 2012 there are no problems:

A := Matrix([[1, 7, 1, 3], [1, 6, 4, 6], [17, 1, 5, 1], [1, 6, 10, 4]]):

n:=4:

z:=add(add(A[i,j]*x[i,j], j=1..n), i=1..n):

restr:={seq(add(x[i,j], i=1..n)=1, j=1..n),seq(add(x[i,j], j=1..n)=1, i=1..n)};

sol:=Optimization[LPSolve](z, restr, assume=binary); 

Can Maple look for the limit of a sequence  f(n)  for n=1,2,3, ... ? Of course, if there is a limit of the function of continuous argument, the limit of the sequence is the same number. But it is easy to give examples of when there is the limit of the sequence, and the limit of the function does not exist:

assume(n, posint):

 limit(sin((n^2+1)/n*Pi), n=infinity);  # Obviously the correct answer is  0

                            -1 .. 1

Why does Maple 2015 solve this very simple system incorrectly?

solve({abs(a-b)=0, sqrt(2*b+c)=0, c^2-c+1/4=0});

With Maple 12 no problem:

solve({abs(a-b)=0, sqrt(2*b+c)=0, c^2-c+1/4=0});

In my  Standard GUI Maple 2015 (32 bit)  on Windows 8.1  plots[spacecurve]  command does not work:

plots[spacecurve]([cos(t), sin(t), t], t = 0 .. 2*Pi);

Can someone confirm this bug?

Can we output a mixed number instead of  an improper fraction in Maple programmatically. For example  

                 instead  of