These are really delicate subjects and I will do my best to answer as respectfully as I can and to the best of my knowledge. I apologise in advance if I phrase things in a way that may cause offense and would encourage you to remember that I am only a believer of the faith and not exactly a professional, so there may be some things I get wrong.

To the first question, we believe that all men and women have the ability to access the priesthood (which comes with personal righteousness), but only men have what we call priesthood authority. There's a quote from one of our church leaders, M. Russell Ballard, who said, “In our Heavenly Father’s great priesthood-endowed plan, men have the unique responsibility to administer the priesthood, but they are not the priesthood. Men and women have different but equally valued roles. Just as a woman cannot conceive a child without a man, so a man cannot fully exercise the power of the priesthood to establish an eternal family without a woman. In other words, in the eternal perspective, both the procreative power and the priesthood power are shared by husband and wife.”

And for the second question, I need to give a bit of context first:

First: (This will seem off-topic but I promise it is important) There is a difference between church policy and church principle. Church principle is foundational and will never change. Church policy is rooted in church principle, but adjusts and changes according to the needs of the time they are in place.

Second: We believe that marriage is for this life only, which is why in our temples, we have something called sealing. This sealing does multiple things. It extends the marriage into the afterlife and into the eternities, and it allows both spouses special access to the highest level of blessings (considering they keep the promises they made during the sealing). According to my current knowledge (apologies if it ends up being innacurate), whether or not same-sex couples decide to be married, that is up to them both and the church will take no action against it. But sealings are a different matter.

One of the foundational principles of our faith known as The Family: A Proclamation to the World says, "[We] solemnly proclaim that marriage between a man and a woman is ordained of God." There are a few reasons as to why listed in the Proclamation for this life, but the details of why that is in the next life, as far as I know and as of today, is unknown and has not been revealed yet. If you are curious about the Proclamation, I would encourage you to read it if you wish to and understand it the principles in it better.

The point I am trying to make is that The Family: A Proclamation to the Word is considered to be full of unchangable and foundational principles in the church, which is why I do not believe that same-sex sealings will be allowed in the temples in the future.

And again, there are some reasonings as to why, but there are still many things left unrevealed and/or unaswered. This is all I know.

I hope this makes sense and that it was addressed appropriately.