Auke1993

Rayquaza cannot Mega evolve with a Mega Stone.
Instead, it can Mega Evolve once it knows the move Dragon Ascent.

All Pokémon listed here can Mega Evolve in the game: https://bulbapedia.bulbagarden.net/wiki/Mega_Evolution
In addition to that, Arbok and Snorlax can Mega Evolve on Pokémon Vortex as well.

The Starter Mega Stones (Venusaur, Charizard, Blastoise, Sceptile, Blaziken and Swampert) can be bought in the PokéMart.
All other Mega Stones can (without someone else's help) only be obtained as Sidequest rewards.

It's possible to trade for Mega Stones, or to purchase them via PokéBay.

It exists, but only in 1 battle in Sidequests.
Crystal Onix is not an obtainable Pokémon.

A pretty simple way is to take Pokémon at their lowest level possible (Lv 6 in the wild), and use them to face their respective training accounts (for example TrainingDarkrai for a Dark-type like Poochyena).
The Pokémon will gain loads of EXP, and with that you'll get a lot of money.
The major money and EXP gain happens once per Pokémon, but with this now Lv. 100 Pokémon you can generally win the battles in 6 turns (1 per Pokémon), making for pretty good money for the time you spent on the battle.

You evolve Rockruff into Lycanroc (Dusk) between 17:00 and 17:59, starting at Level 25.

Mewtwo (Evolution) is only available via the Discord Quizzes.
However, some people that win these Pokémon may put them up for trade or auction. So you could try to buy or trade for them.
It's very likely that Mewtwo (Evolution) will be very expensive though.

Beast Balls work similarly to Master Balls, except for the fact they only work on Ultra Beasts.
Beast Balls will always capture the Ultra Beast when thrown.

You have to open the Event Center.
In there, there is a button to choose which Genesect to transform into Genesect (Ice).

It was likely put to the side, that's an option for those that don't want to have it active.
You'll likely have a small arrow symbol on a button in the bottom right corner of Vortex, pointing left.
Clicking on that will likely open the chatbar for you.

This is a list of Pokémon locations: https://wiki.pokemon-vortex.com/wiki/List_of_Pokemon_By_Location

In Sidequests, you get rewards once you finish a region. You can find details about it here: https://wiki.pokemon-vortex.com/wiki/Sidequests

The Event Center can only be unlocked during some events. As there is currently no event going on that uses the Event Center, it is closed as it would have no purpose at this time.

You are correct.
Trainer Battles currently give double EXP.
You can find this info (and other event info) on this page: 
 

The skill tree currently doesn't do anything.
It's likely something that will be implemented in the future.

100 people in the clain is the limit.
Originally, this limit did not exist. This meant that clans could have more than 100 members.
I cannot remember the details on how members would have to be removed, but I know more cannot be added to such clans.

You can change your clan avatar in-game by linking your Vortex clan with your Forum clan (of the same name).
After that, changing the avatar on the Forum will change it on Vortex.

Evens always end at the listed time at server time, which is the time in Britain.

You are able to encounter Alolan Forms and evolve into Alolan evolutions when you are in the Alola region in Sidequests.

There seems to have been a Discord server problem.
Things seem to be back in working order, although VortexBot will need to be reset before the Quiz can work again.
Other features of VortexBot seem to work.

Yes, there certainly are ways to do that. Training accounts are a good way to quickly gain EXP.
I recommend watching this video, as it details a lot of different ways to earn EXP, and how different kinds of Pokémon earn EXP the quickest.
 

It used to be possible to battle against 3 of the Vortex Admins, who had very powerful teams, all at Level 150.
I don't know if, and when, they will make a return.

Melmetal is an evolution of Meltan, so evolving Meltan is likely the only way to obtain it.
All others likely to be event exclusive Pokémon.

A 'ping' is when someone uses the @ symbol with a word, role or your name in a way that gives you a notification or a number next to the channel, to let you know someone likely wants something from you, or wants to notify you of something.

It deletes it for everyone.

It means you're playing on an IP where multiple people play.
A school or library is place this can happen at.
To get the daily log-in reward for yourself, you'll have to be the first of everyone on the IP to log in.

I believe it was because it wasn't used by that many people, and because it caused some server problems from time to time.

Every trainer battle counts. This means Gym Leaders count as well, as they are also trainers.

Pokémon obtained via codes show up in the game as well in the 'caught/obtained' box.
These can be from events, but also from the Vortex store.