It's important to know that versions 2.0 and 2.5 are identical in terms of game mechanics and system changes, the difference is that 2.0 was the updated arcade version only released in Japan while 2.5 is the PC Steam port. You can tell what version of the game footage is by looking at the timer at the top of the screen, 1.1 matches have a blue timer while 2.0 and 2.5 matches have a white timer.

1.1 Aigis has higher damage, and consumes less Orgia gauge with all attacks (For example 1.1 Orgia Dash uses at least 20% orgia, while 2.5's Dash uses 25%). On the bright side, 2.5 Aigis has a lot faster moves in neutral such as mortar and 2C. Overall she was nerfed, but so was everyone else so it's not too bad. Almost all of her 1.1 combos will work in 2.5, but with about 30% less damage.
Her tiering placement actually rose in the change, from about 5th in 1.1 to arguably 3rd in 2.5, though some players argue she's trash now, largely due to a lack of character representation in the west.
To read more about her changes, check out the Aigis 2.5 Dustloop Character wiki[www.dustloop.com] and Patch Notes[www.dustloop.com]

Shadow Aigis:
Aigis is one of the only characters in 2.5 with a Normal form that can keep up with their Shadow form. Every other character (Besides arguably Narukami) has a far superior shadow version, but Aigis' shadow is a well balanced counterpoint to Normal Aigis. S.Aigis has a larger focus on meter/Orgia management for the benefit of nuclear damage output at 100 Meter and meterless double mode change combos. Shadow also always has access to awakening spear (214214A) which is an extremely quick and powerful reversal option. The main downside of Shadow Aigis is less damage and her albeit incredible autocombo consuming bullets, which can be frustrating in prolonged matches.
Normal Aigis of course has the flat 10% damage boost, and a useful autocombo of her own which leads into good mode change routes/corner shenanigans. Both Aigis forms are likely top tier, and there's no clear consensus for which is better. Just pick your favorite.

These terms will be used repeatedly, so here's what they mean.

• oad = Orgia Air Dash. j.AB while in Orgia Mode
  
• hover = j.2AC
  
• air turn = j.AC
  
• ml = mortar loop. 214A/B > hover > 214A/B > hover, while in Orgia Mode.
  
• spml = sp mortar loop. 214AB > hover > 214A/B > hover, while in Orgia Mode. Costs 25 SP

Here's how to understand Numpad Notation [www.dustloop.com] but in essence just treat the numbers as directions on a phone number pad. Like 236A means Down Down-Forward Forward A.

Ultimax doesn't explain what ABCD are, but they're just the attack buttons.
A B C D
So 236D would just be
Simple, eh?

Unfortunately, Aigis is pretty terrible without the threat of Orgia. Her entire gameplan outside of it is to either confirm into a mode change combo or stall the opponent with midscreen zoning and her long autocombo. Avoid entering burnout at all costs, because Aigis is completely helpless when Orgia is off the table.
236[-B] was listed as -B instead of B because steam guides interprets B surrounded by [] as bold formatting.

Corner Mode Change Combos

Corner Orgia Combos

Because of her new speed and increased Orgia usage, most combos benefit from disabling Orgia mid combo. This allows you to recharge the Orgia gauge as you combo them, and re-enable it for the finishing blow.

Here's the link to the 2.5 Dustloop wiki Aigis combo page, https://www.dustloop.com/wiki/index.php?title=P4U2.5/Aigis/Combos, there's videos of each of the combos discussed there. I also wrote that page, so that's why so many of these combos come from there.

If you're trying to improve with any character in this game, or just want a community to play with, try joining the P4AU Fightclub Discord channel. Google it because steam doesn't like discord links.