Agreement depends on tense, and past, present and future tenses are relatively easy to distinguish:
I can do whatever I want to do. (both present tense)
I could do whatever I wanted to do. (both past tense)
I could have done whatever I [would have] wanted to do. (present perfect and past)
I will do whatever I want to do (future and present)
Without additional context, all that can be assumed from this construction is that some reading occurred. There is not enough information to infer how much was read, and the construction does not imply completion of anything beyond "the act of reading".
Contemporary describes some point in the past, but the surrounding events are present tense relative to the time period. For example, contemporary music in the 1930s was jazz, where as contemporary music now is pop.
In the same context, you can reference an event in 2017 and speak of the contemporary (which will refer to 2017) social climate.
They're both correct.
The main difference between them is that the first one implies that the son doesn't play video games much any more; the second one leaves this question open.
Merriam-Webster dictionary defines used to as:
used to say something happened repeatedly in the past but does not happen now
The premise of this question is based on a couple of false assumptions.
As a verb
The present tense of the verb unassigned is unassign. It's not as common, but it's perfectly reasonable to apply the un- prefix to some verbs in order to form their opposite.
From "Assign and unassign" at Pearson:
Assign and unassign
You can unassign an assignment ...
a statement, pattern of behavior, a prototype, a "first" form or a main model which other statements, patterns of behavior, and objects copy, emulate or "merge" into. (Frequently used informal synonyms for this usage include "standard example", "basic example", and the longer form "archetypal example". Mathematical archetypes often appear as "...
after finding out
This is correct because "finding out" is an event (a noun, more or less) based on "finding" (with '-ing') being a gerund, or "verbal noun", and therefore doesn't need to be a verb with a subject.
But, "found" is not a gerund, so it behaves like any other verb; it needs a subject. In order to be correct, "after found out" would need to be ...
This is a 'complex sentence' (that has a main clause and minimum one dependent clause).
The first clause is Past Continuous, and the second one, in Simple Past tense. This structure implies "when an action took place, the other was progressing."
Here, both clauses have a common subject. It is similar to "While watching the movie, I forgot the bus-timing."
The crucial thing is that the last but one syllable of "vomited" has no stress. Not even secondary stress. So the final consonant doesn't double. By contrast, the last but one syllable of "emitted" has stress (because the last syllable of "emit" has stress).
This issue is raised in this question, to which a good answer is given.
(No stress) ...