Diagram:
The only variable we do not know the placement of is M and the order of the PT/TP block.
M is a free agent/floater/random in this game and it places an important role in the two questions you have.
#8.
The question stem tells us that M and G are separated by exactly one variable. Notice that we either have M_G or G_M.
We could never have a situation of G_M because we do not have enough variables to accomplish this. After M is placed, no more variables can come after G, all must come before. So this scenario is out.
That means that we must have M_G.
The M is placed, so we must go with our sequencing tree we have in our global diagram. We now know that the L must come between the M and G. The L is the closest variable to G. We know that the F will be first and that the PT/TP block will come after it. However, the order of that PT/TP block is not solved by a mere sequence of M_G, this we only know the exact placement of four variables because P and T are not known.
#12
With P going fourth, we know that only two variables can go after it. Looking at our sequencing tree we know that it must be L and then G. T could not come after P because where would L and G go? Same with M. Where would L and G go? Not enough room.
We know that T must come directly before P now. So that will be the occupation of the third slot. However, now we are caught in uncertainty. We know that F must come before T, but it does not have to come immediately before T. And we know that the placement of M is a random thing, thus we do not know for certain where F and T go. This is shown below by the box that can flip the placement of M and F.
