It seems that applyrule cannot handle variable numbers of arguments, and I cannot use something like 

applyrule(f(u::anything, v::seq(anything)) = g(v, u), [f(x, y, z), f(x, y, z, t)]);
 = 
                  [f(x, y, z), f(x, y, z, t)]

Strangely, Maple does support the identical patterns in parameter declarations: 

eval([f(x, y, z), f(x, y, z, t)], f = ((u::anything, v::seq(anything)) → g(v, u)));
 = 
                  [g(y, z, x), g(y, z, t, x)]

So the two designs do not appear coherent. Should this be regarded as a "bug" in a sense? 

Of course there is no need to use the  modifier; here it is enough to use 

evalindets([f(x,y,z),f(x,y,z,t)],'specfunc'(anything,f),w->g(op(2..(),w),op(1,w))):

use f = MakeFunction('g(args[2 .. ], args[1])') in [f(x, y, z), f(x, y, z, t)] end:

use f = unapply('g(_rest, _w)', [_w::anything]) in [f(x, y, z), f(x, y, z, t)] end:

But the problem is, why is there such inconsistency described above? 

Although I still prefer applyrule (as evalindets/subsindets is not as intuitive as applyrule),  I have heard that it is regarded as being more or less antiquated in modern Maple. I notice that a lot of (yet not all) examples given in the help pages of evalindets/subsindets can be reformulated by applyrule, but does any use of applyrule also correspond to using evalindets/subsindets? And if so, how to equivalently rewrite those transformation rules (especially complicated ones like nested function applications) in the syntax of evalindets/subsindets?

For example, I would like to draw the following figure in Maple.

(The above figure is taken from MatLab's documentation.) 
Here are these four graphics objects: 

use plottools, ColorTools in
	l0, l1 := line~([<1 | 0>, <1 | 1>], [<6 | 5>, <6 | 6>], 'color' =~ Color~(["#0072BD", "#D95319"]))[];
	r0, r1 := rectangle~([[2, 0], [4, 0]], [[3, 6], [5, 6]], 'color' =~ Color~([[.6, .7, .9], [.95, .7, .6]]))[]
end:

However, either 

`plots/display`([r1, l1, l0, r0], 'axes' = "boxed", 'size' = ["default", "golden"], 'style' = "patchnogrid")

or 

`plots/display`([r0, l0, l1, r1], 'axes' = "boxed", 'size' = ["default", "golden"], 'style' = "patchnogrid")

outputs the same graphical image where the lines are always rendered on top of each rectangles instead of the other way around.

 

So how to superimpose the right rectangle over the two lines? To put it differently, how to handle the graphics hierarchy? I have read some similar questions like Order in plots:-display - MaplePrimes, yet I cannot find any workarounds. 

Note that in my opinion, the result should comprise two unbroken line segments rather than four subordinate line segments! 

For example, here are two equations containing trigonometric functions (Note that they do not form one system!): 

restart; # There are more examples, yet for the sake of briefness, they are omitted here. 
eqn__0 := cos(x)*cos(y)*cos(x + y) = 2*(sin(x)*sin(y) - 1)*2*(sin(x)*sin(x + y) - 1)*2*(sin(y)*sin(x + y) - 1):
eqn__1 := (cos(x + y) - (cos(x) + cos(y)) + 1)**2 + 2*cos(x)*cos(y)*cos(x + y) = 0:

Unfortunately, none of 

(* Tag０ *) RealDomain:-solve(eqn__0, {y, x}):
(* Tag１ *) solve(eqn__0, {y, x}) assuming y + x >= 0, (y, x) <=~ Pi:
(* Tag２ *) RealDomain:-solve(eqn__1, {y, x}):
(* Tag３ *) solve(eqn__1, {y, x}) assuming y + x >= 0, (y, x) <=~ Pi:

outputs concise solutions.
Using `plot3d`, it is easy to check that when "And(y + x >= 0, (y, x) <=~ Pi)", “{y = Pi/2, x = 0}, {y = Pi/3, x = Pi/3}, {y = 0, x = Pi/2}, {y = Pi/2, x = Pi/2}” is both the only solution to "eqn__0" and the only solution to "eqn__1". But how to get Maple to do so without manual intervention?

Edit. The main purpose is to automatically find the generic solutions to each of the two equations (Tag０ and Tag２) (separately). Now that the cosine and sine functions are both periodic with period 2π and both (lhs - rhs)(eqn__0) and (lhs - rhs)(eqn__1) are even symmetric, it is enough to focus only on the region y + x ≥ 0 ∧ (y, x) ≤~ Pi. So, in theory, a second-best workaround should be Tag１ and Tag３. However, why is Maple still unable to find the four exact solutions above?

The help page mentions: 

But what about the so-called q-hypergeometric function? Though there exist QDifferenceEquations:-IsQHypergeometricTerm and QDifferenceEquations:-QHypergeometricSolution in Maple, they do not seem to represent the function itself. 
For example, how to type the q-Gauss sum (cf. DLMF's §17.6(i)) or verify the last “simple series expression” given in Basic hypergeometric series - Wikipedia? In Mma, one may achieve these with something like 

, 

while 

convert("QHypergeometricPFQ[{a, b}, {c}, q, c/(a b)]", 'FromMma', 'evaluate');
 = 
                              /                 c \
            QHypergeometricPFQ|[a, b], [c], q, ---|
                              \                a b/

So has the q-hypergeometric function been implemented in Maple?