Post (the prefix not the cereal brand)
after
Mixed up
Opposites if you go in order
still mixed up
100

A test at the end of a unit. (postwar, posttest, prepare)

What is posttest?

100

The time of day between noon and evening. (aftertaste, afterword, afternoon)

What is afternoon?

100

Of an era before recorded history. (foretell, prehistoric, posttest)

What is prehistoric?

100

Period before regular league games begin (postseason, preseason, afterthought)

What is a preseason?

100
The time of day between noon and evening. (precede, postdate, afternoon)

What is afternoon?

200

To date anything later than the actual date. (postseason, prefix, postdate)

What is postdate?

200

Flavor left in the mouth after food or drink. (afterword, postdate, aftertaste)

What is aftertaste?

200

Workman in charge of a department. (preposition, foreman, afterthought)

What is a foreman?

200

Period following the regular schedule in sport. (postseason, preseason, afterword)

What is the postseason?

200

Come before or go before (postpone, afterword, precede)

What is precede?

300

A time of peace after a long period of battles. (postwar, preface, postdate) 

What is postwar?

300

Something done or considered later. (afterword, afterthought, precede)

What is an afterthought?

300

A syllable in front of a root word. (postpone, prefix, afterword)

What is a prefix?

300

Precaution or planning in an action. (afterthought, forethought, posttest)

What is forethought?
300

To predict what will happen in the future. (posttest, foretell, afterthought)

What is foretell?

400

Period following the regular schedule in sports. (postdate, postseason, afterthought)

What is postseason?

400

Information at end end of a book. (afterword, afternoon, prehistoric)

What is an afterword?
400

Male ancestors, founders (forefather, postwar, aftertaste)

What is a forefather?

400

Something done or considered later (afterthought, forethought, posttest)

What is an afterthought?

400

A word expressing a noun's relation to another word. (postpone, afterword, preposition)

What is a preposition?

500

To put off until another time. (postpone, postdate, postwar)

What is postpone?

500

Mint leaves a fresh __ in my mouth.

What is aftertaste?

500

Seeing ahead, planning for the future (foresight, preseason, postseason)

What is foresight?

500

2 parter: 1 To get make or get ready or to arrange. 2 To put off until another time (foreword, postpone, prepare)

1 What is prepare?

2 What is postpone?

500

To date anything later than the actual date (precede, postdate, afterword)

What is postdate?