Multiple questions

[Kezeal]

Once again I decided to start a project, but this time I seriously wish to finish it. It's about time I finish something I start.
The problem I previously always ran into was that spriting took so much time that I got bored of the entire project, so this time I'll start with coding and maybe even skip spriting completely, just copy-pasting something.
Anyway, back on topic, here are the questions:

1. Is it possible for a character to freeze others infinitely, so that they wouldn't automatically unfreeze? It would still be possible to free them by simply hitting.

2. Is it possible to make "slippery" ice on the ground, so that the characters fall down and then begin to slide on it while lying down, only getting up after they have slid over the ice?
2.1 If yes, then would it be possible for one character(or the creator of the ice) to not be affected by it?

3. Would it be possible to create a kind of an ice version of Firen's flamewalk, but instead leaving behind a trail of ice which will have question 2's effect and makes the character run faster? Kind of like iceskating.

4. Is it possible to create a move when the character is in mid-air, then he could create a small platform of ice to his left/right and boost himself from it? Simplified - jumps up and gets boosted to the side.

5. Is it possible to create something like John's shield, but lasts longer, doesn't hurt others, nothing bounces back(everything gets destroyed/stopped) and is summoned on left and right?

6. Is it possible to create an 'arc' of ice that can not be rolled through? Kind of like a semi-circular wall that nothing can pass(except that sneaky Woody, of course. Highly doubt you can defend an area from getting teleported into).

[Alblaka]

1. Is it possible for a character to freeze others infinitely, so that they wouldn't automatically unfreeze? It would still be possible to free them by simply hitting.

If you mean freeze as in the actual 'frozen' frames, no.
You could, however: Spawn new freezing projectiles into them before they naturally thaw, causing them to be re-frozen. The freezing animation & sound would play every time, though.
Alternatively, you could create a 'timefreeze' effect by hitting (a group of) enemy(s) with itr/king:0 fall:-1 vrest: 1. They wouldn't be able to move or do anything and get stuck in their current animation.

2. Is it possible to make "slippery" ice on the ground, so that the characters fall down and then begin to slide on it while lying down, only getting up after they have slid over the ice?
2.1 If yes, then would it be possible for one character(or the creator of the ice) to not be affected by it?

You can easyly create an 'ice layer' that will cause everyone (hostile) touching it to 'slip', aka be knocked down. With some itr/kind:3 action it could be possible to create the desired 'sliding' effect, by 'holding' the enemy in his falling frame and moving him along the ice. Would be buggy though, I suspect.

3. Would it be possible to create a kind of an ice version of Firen's flamewalk, but instead leaving behind a trail of ice which will have question 2's effect and makes the character run faster? Kind of like iceskating.

Ice version of flamewalk is definitely possible, same to adjusting it's speed and the projectiles spawned.

4. Is it possible to create a move when the character is in mid-air, then he could create a small platform of ice to his left/right and boost himself from it? Simplified - jumps up and gets boosted to the side.

Mid-Air jumps are possible, you can just give him the move as a hit_xy tag in his jumping frames. It's not much diffrent from any ground-based dash move, except for it being executed mid-air.

5. Is it possible to create something like John's shield, but lasts longer, doesn't hurt others, nothing bounces back(everything gets destroyed/stopped) and is summoned on left and right?

I don't think this specific request is possible. Creating a shield that destroys any projectiles isn't difficult, but it would as well hit any enemie players. Alternatively you could create a shield that does only bounce back projectiles and ignores player, but it will reflect the projectiles, not destroy them.
You could, however, create a shield that acts as a blockade (think of it like a stone or crate), that will block player and projectile movement. Projectiles wouldn't be destroyed, but would get stuck at the shield till it runs out.
Speaking of which, altering the duration of the shield is no big deal at all.

6. Is it possible to create an 'arc' of ice that can not be rolled through? Kind of like a semi-circular wall that nothing can pass(except that sneaky Woody, of course. Highly doubt you can defend an area from getting teleported into).

Yes, itr/kind:8 (if I remember the number right) creates a movement-blocking zone. It's not foolproof though, anything without a bdy can pass through (f.e. rolling characters or invisible rudolphs as well as specific projectiles (none of the vanilla LF2 ones though)). But it's pretty simple in itself.

[YinYin]

1. Is it possible for a character to freeze others infinitely, so that they wouldn't automatically unfreeze? It would still be possible to free them by simply hitting.

Kinda ... you can catch and hold them in frame 201 while allowing them to get hit. Will go wrong with large characters though. You could counter that by adjusting the catching object to correctly hold large frozen characters (Knight and Julian basically) and give it an ice base image smaller frozen characters will appear to be standing on (so they don't seem to float). The large ones should just cover it.

Have a look at Siegvars frozen for reference of how to create such objects. (catch + DJA creates an object that holds the opponent)

2. Is it possible to make "slippery" ice on the ground, so that the characters fall down and then begin to slide on it while lying down, only getting up after they have slid over the ice?
2.1 If yes, then would it be possible for one character(or the creator of the ice) to not be affected by it?

Yes. Again a cpoint object could do the job. May be pretty difficult though.

3. Would it be possible to create a kind of an ice version of Firen's flamewalk, but instead leaving behind a trail of ice which will have question 2's effect and makes the character run faster? Kind of like iceskating.

Of course!

4. Is it possible to create a move when the character is in mid-air, then he could create a small platform of ice to his left/right and boost himself from it? Simplified - jumps up and gets boosted to the side.

Yes. Easily.

5. Is it possible to create something like John's shield, but lasts longer, doesn't hurt others, nothing bounces back(everything gets destroyed/stopped) and is summoned on left and right?

Yes. May be difficult though. You could have a look at Harlequins shield.

6. Is it possible to create an 'arc' of ice that can not be rolled through? Kind of like a semi-circular wall that nothing can pass(except that sneaky Woody, of course. Highly doubt you can defend an area from getting teleported into).

No. Unless you edit all characters to have special bdys in their rolling frames.

@Alblaka: duuude! edit: so many flaws in your answers :p

[Alblaka]

Hmmm, wasn't it buggy to hold enemies in frames that do not contain cpoints and the proper caught-state on their side?

[Kezeal]

Thank you for your answers. I am not going to mark it as "Solved" yet, I'll do that after I have figured out the small things on how to do it and have finished those things. I am sure I will come back soon with more questions about the same things.