Momentary vs Temporary

Limited is very different to short.

Momentary: Lasting for a very short time; brief. ¹
Brief == not lasting for long.

Temporary: Lasting for only a limited period of time; not permanent. ¹
Limited == restricted in... amount (But has no defined amount of time it is limited for).

Momentary is a very short period of time. Temporary means it can be there indefinitely - not necessarily planned, but it will stop existing at some point.

The second hand was momentarily pointing to 12 ²

Versus

The scaffolding is on the house temporarily, while they have their roof redone. ²

^{1: Google Dictionary, momentary and temporary. Brief and Limited.
2: My Quotes}

Momentary means "just" touching -- as when a billiard ball bounces off another.

{So, depending on the physics of the situation involved, it's "just" touching. So, two billiard balls "momentarily" touching is 0.1 seconds (or whatever that is - ask an engineer). Whereas - for example - imagine describing a naval collision during a battle: the two ships "momentarily" touching (imagine all the grinding of metal, etc) would likely physically occur over - let's say - some 10 seconds. For people who work with continental plate tectonics, a "momentary" touch might be 100,000 years.}

Temporary simply means "not permanent."

Temporary has utterly no connection to whether short or long.

You know, like a "temporary teacher" or "the temporary offices" or "a temporary 87 million year break in the galactic cycle" or whatever.

BTW the answer to your question at the end, is of course sentence (1)

My team's requirement for implementing ABC system is temporary.

(FTR that sentence is generally completely meaningless if you use the word momentary - unless, bizarrely, you were talking about database transactions or something obscure.)

A momentary action takes less time than a coffee break. In the work place, any momentary thing should be something that would go unnoticed by anyone currently taking a coffee break.

Temporary is an arbitrary amount of time, and could even be used to replace momentary in many cases, but it does not give the implied connotation of quickness like momentary does.