Does everyone have a grand trine?

Not everyone has a grand trine. Only some people do, and some people even have multiple grand trines (likely within the same element). Trines with angles like the ascendant or midheaven can also be considered for a grand trine.

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What is your Profection year?

Using the whole sign House system, starting with the Rising Sign in the 1st House, this will be a 1st House Profection Year for your first year after birth. Then in your second year, you will move into a 2nd House Profection Year and so on. Every twelve years you will come back to the same House Profection. Is quincunx a good or bad aspect? The quincunx, however, is an "it does not compute" aspect. The wants and needs of the two signs involved have no real connection-instead it's a disconnect. They're unrelated by element or mode, so there's no natural point of contact, no easy affinity or resonance.

What aspect is 150?

An aspect of 150 degrees between two planets. Also, what is the difference between conjunct and inconjunct? As nouns the difference between inconjunct and conjunc. is that inconjunct is (astrology) a quincunx while conjunct is (logic) either term of a conjunction.

Is it possible to have three Stelliums?

Absolutely. But you haven't really described two stelliums in your question. The planets need to be close to each other to create a stellium - 3 or more planets - within about 8 degrees of each other - giving the Sun and Moon about 10 degrees to reach another planet in the sign or house.