Okay, I think I can answer most if not all. And sorry if some answer is based on links rather than typed.
1. Here is the list of the tutorial from Oshare Keiji
1.) Explanation Of Match Types (Single, Tag, 3-on-1)
2.) Explanation Of Screen Icons (Timer, LP Gauge, SP Gauge, Ride Ratio, Enemy Detector, Armaments)
3.) Test: Move in 8 Directions using D-Pad.
4.) Test: Perform a Double Jump (X two times) then float. (Hold X)
5.) Test: Lock on to an opponent. (L Button)
6.) Test: Toggle Lock on between two opponents (L two times)
7.) Test: Battle Basics. Defeat your opponent. (You are unarmed for X and Triangle, but you have a Hellgate Blaster Machine Gun on Circle)
8.) Test: Quickstep in 8 Directions by pressing D-Pad twice on each direction.
9.) Test: Dash 3 times. (Any direction)
10) Test: Perform an Attack Chain. The best way to do this is to tap Square, press R while you're shooting, then follow up quickly with Circle or Triangle (Aero Vajra or PicoPico Hammer)
11.) Test: Guarding. Hold R and wait for the opponent to attack you 3 times.
12.) Test: Just Guard. Wait for the enemy to shoot, then guard at the exact second that it's about to hit you. Timing is everything.
13.) Test: Turning. Press Square and X together 3 times.
14.) Test: Knockdown Recovery 1. Press X and any directional key.
15) Test: Knockdown Recovery 2. Press Square, Circle or Triangle.
16) Test: Vertical Dashing: Press Up, R and X simultaneously to go up, and Down R and X together to go down. You have to do three sets of both in rapid succession with no gaps between up and down.
17.) Test: Ride Ratio 1: Attack the enemy until your Ride Ratio maxes out.
18.) Test: Taunting: Press R and Triangle simultaneously 3 times.
19) Test: Rail Action. Perform all 4 of the pre-programmed Rail Actions. (Up/Down/Left/Right + Triangle and Circle simultaneously) Attack your opponent so your SP gauge recovers quicker.
2. Quoting from Oshare Keiji "Rail Action is a programmable Evasion/Attack pattern for your Shinki. These actions use SP and up to four can be equipped (second option in the main equip menu) Evasive actions are known as Routes, which makes the Shinki move out of your opponent's aim and perform directional maneuvers at twice it's normal specs. Attack actions are weapon specific, also messes with lock-on, and gun-based ones do not use up ammo. they cannot be performed if you do not have the correct weapon type."
So Rail Action is already programmed and you can't edit it. There are three types of RA (in here, most people just call them RA then Rail Action). Move (Evasion or repositioning), Atk (attack RA specific to a weapon) and Ultimate (special attack specific to each shinki). For Move and Atk, you need to get it by facing an opponent that have that move. Your shinki will randomly memorize and learn it. Ultimate however is different. You need to finish all her event and use specific parts to use it.
3. It depends on the shinki. Some double her speed, while some double her attack. One characteristic that all have is, when Ride max (100%) All SP cost is cut to half.
Here is the list of shinkis and what they doubled
Arnval Mk2 ++ Speed, Defence, Weapons Reload
Strarf Mk2 ++ Attack, Weapons Reload, Guard Break Damage
Howling ++ Defence, Speed, Guard Break Damage
Maochao ++ Attack, Weapons Reload, Speed
Zelnogrard ++ Attack, Weapons Reload, Guard Break Damage
Fubuki ++ Attack, Speed, Guard Break Damage
Ach ++ Speed, Attack, Guard Break Damage
Yda ++ Defence, Speed, Weapons Reload
Altlene ++ Attack, Defence, Guard Break Damage <-----She is my favourite and basically, a walking/flying fortress.
Altines ++ Defence, Weapons Reload, Speed
4. Attack Chain: Press R in the middle of using a weapon and press another weapon button for a quick switch. Hope someone else can find a better solution.
5. If you like that kind of attack my recommendation is either dual dagger, gloves and one handed sword for melee (because of their speed) and handgun or machine gun (for speed and also a good to increase ride bar) and shotgun (for justice shot, where at point blank will do MASSIVE damage. But a bit slow).
Shield in this game won't block attack. They will only give resistance to some attack element and give some skill for your shinki.
If you want a shinki that is BOTH fast and strong, and with Speed to outmaneuver and decent defence, look no further than Ach. She is perfect for your style of playing.
6. You need to buy her head gear. ヘッドセンサーユニコーン. It is the only head gear where she will keep her long hair. Other shinki also suffer this where they suddenly lose their long hair in other headgear except for their respective head gear.....with the exception of Altlene who kept her long hair in almost every head gear available.
7. Sure, why not
Does Ach's equipment come in White too at least?