a) This is a linear homogeneous recurrence relation with constant coefficients of degree 2.
b) This recurrence is not homogeneous because constant on right side
c) This recurrence is not linear. because of power $a_{n-2}^{2}$
d) This is a linear homogeneous recurrence relation with constant coefficients of degree 3.
e) This recurrence does not have constant coefficients so not linear
f) This recurrence is not homogeneous.
g) This is a linear homogeneous recurrence relation with constant coefficients of degree 7.
for more detail you can follow this link
https://gateoverflow.in/339065/kenneth-rosen-edition-7th-exercise-8-2-question-1-page-no-524