Learn English – Adjective for not knowing any better

In this year is a prepositional phrase with this year as the object. This year by itself is a noun phrase.

Both can be used to place an event within the current year, but this year is much more natural. (I don't think in this year is a hypercorrection.)

In this year, Tommy has grown 12 inches. (odd)

This year, Tommy has grown 12 inches. (ok)

But if we're not talking about something happening but counting the number of days in a particular span of time, the preposition is necessary.

She left him this year. (ok - she left him denotes an event)

How many days are left this year? (very odd - left is an adjective)

How many days are left in this year? (ok)

Expressions telling when are sometimes prepositional phrases (during exams), sometimes adverbs with or without modifiers (later, very soon now), and sometimes noun phrases (next Tuesday, this year).

The two examples you give seem to me quite different. In the first case, you're saying that you've done them a favor and they owe you, and yet you politely word requests in a deferential manner. The famous actor example seems quite different, like they have to give him what he wants because he's rich and famous and powerful, not because he has done anything for them personally.

"Oily" and "smarmy" are definitely NOT appropriate terms for the first case. Both have very negative connotations. These words are normally used to describe a salesman or a politician who pretends to really care about the other person but is in fact being completely selfish and usually deceitful.

Perhaps words that would fit here are "unassuming" or "unpretentious". These mean to not take advantage of one's position or to insist on the respect or deference that one is arguably entitled to.

The case of the actor seems entirely the opposite: he is demanding excessive respect for his social status. I'd call that "pretentious" or "presumptuous".