A tournament consists of best of three games in a set umber of rounds. The standard is 6 rounds, with the Top 8 players competing at the end of the tournament.
As found on the Wizards website:
Constructed Tournament
Tournament Length
Number of Swiss rounds based on attendance according to the following chart:
Swiss Rounds9 - 16417 - 32533 - 64665 - 1287129 - 2268227 - 4099410 or higher10
Advancement
You can find a Magic: The Gathering tournament locator on the official Wizards of the Coast website or by using the Wizards Event Locator tool.
The pace of play in Magic: The Gathering is sometimes considered too slow for tournament standards, as players have a limited amount of time to make their moves.
The legal Magic: The Gathering sets for tournament play are determined by the format of the tournament. The most commonly played formats are Standard, Modern, Legacy, and Vintage. Each format has a specific list of sets that are legal for use in deck construction. It is important to check the official Magic: The Gathering website or tournament guidelines for the most up-to-date information on legal sets for each format.
Altered art cards are allowed in Magic: The Gathering tournaments as long as they meet certain criteria set by the tournament organizer, such as being recognizable as the original card and not providing any strategic advantage.
I presume that you mean tournament packs. If so they are random.
The official ruling on the Nexus of Fate card in the current Magic: The Gathering tournament format is that it is banned in Standard and Historic formats, but legal in other formats like Commander.
The standard deck size for tournament play in Magic: The Gathering (MTG) is 60 cards.
In a Magic: The Gathering tournament, 2HG Sealed rules require each team to build two decks using six booster packs. Each team shares a life total of 30 and takes turns playing together against another team.
The official ruling on the use of "Wish" cards in Magic: The Gathering tournaments is that players are allowed to use them, but they must adhere to the tournament rules and guidelines set by the event organizers.
Yes, you can sacrifice a creature at any time in Magic: The Gathering as long as you have a card or ability that allows you to do so.
Till someone destroys them
No, Riot does not stack in Magic: The Gathering.