Newbie Question - Granting Playable Character Status Immunity

I've never tried to hack this game before and every piece of advice I've read has said to start small, so I'm starting with what I hope is a trivial question.

I was looking to make a single, permanent playable character immune to a specific negative status. For example, I would like to make Edgar immune to Poison inherently so that he could not be poisoned at all under any circumstances. My questions follow as such:

1. Is this a simple task or an advanced one?
   
2. Would I have to permanently force the equipping of a Relic to achieve this effect or could this be done in a different way?
   
3. Can this be done through good, old-fashioned Hex editing, or will this require ASM work?
   

will this require ASM work?

Yes, you could at the beginning of the battle (as an example when equipment/relics properties are set for the characters but it could be done elsewhere) make a conditional on Edgar actor ID and force the immunity of a status.

This may be a pointless bump, but with the benefit of hindsight, I can answer my ignorant, former self. I'm a little tougher on past-me than I am on others, but past-me needs tough love.

I was looking to make a single, permanent playable character immune to a specific negative status. For example, I would like to make Edgar immune to Poison inherently so that he could not be poisoned at all under any circumstances. My questions follow as such:

1. Is this a simple task or an advanced one?
   
2. Would I have to permanently force the equipping of a Relic to achieve this effect or could this be done in a different way?
   
3. Can this be done through good, old-fashioned Hex editing, or will this require ASM work?
   

1. This is hard to say without knowing your skillset, but from the questions you have asked I can gather this would be intermediate to advanced for you.

Final Fantasy VI does not have character-specific immunities coded in or even intended to be coded in.  Not only would you have to create a check for a character, you would have to create custom code to set the immunity. That you ask if this is a simple task means you don't know how the code works. The actual solution is a simple code addition, but the thought process to get there is not trivial.

2. Forcing a character to equip a Relic in of itself is somewhat involved. It could work, but you would be handicapping a player by forcing that character to only be able to use one Relic slot. What you would like to do can definitely be done in a different way...but it will take more work.

3. Definitely ASM work, and that you're asking this means you don't have a strong grasp of what hex editing is. It also indicates you don't have a strong idea of how battles work in Final Fantasy VI. Before you can edit you have to be able to understand how the game works and the limits of what you can do.

By "hex editing" I assume you mean just modifying existing hex values, since ASM work really is just more involved hex editing. Modifying existing values can be used to clear or change behavior that is already present in the rom. For instance, you can use a hex editor to change an assigned palette by changing the corresponding byte, or you can change an action with a variable success rate into a steady one. However, this type of editing cannot append behavior with new behavior.

Once again, Final Fantasy VI, in its battle system, never sets a status immunity based on the character itself, only equipment. By definition, this type of change would require ASM work.

Let me say that this is a great idea that would be neat to implement, but this can't be achieved by toggling bytes. You'd have to write custom ASM code to account for this behavior, and if you are not comfortable with this you will not be able to make this change.

By the way, I'm no expert. I have not made the modification you describe either, but I want you to  rough idea of what you need to know.