Bards And Scrolls

Okay so I've been perusing the boards and while some of my questions have been answered to a degree I wanted to get some better clarification here.

So, I'm playing a 9th level Arcane Duelist Bard and have just come round to being able to afford some of the tastier scrolls. Also previously hadn't been looking at scrolls much as I was happy with my own spellcasting and so forth. (Also apologies if any of these are tragically basic I just can't figure them out so thought I'd ask)

So a few questions.
First off do spells cast from Scrolls incur Arcane Spell Failure? As an arcane duelist I'm looking at ending up in full plate so probably won't bother until I've found a way round it.

Secondly (and I saw a thread on this that didn't seem to come to a conclusion): If I cast a scroll written by a wizard do I have to use INT for the prerequisite stat line and resultant DC? Obviously as it could have been scribed by a sorceror and found scrolls are only ever differentiated by arcane and divine and not by individual spellcaster.

Which brings me to, thirdly: Can I use UMD for divine scrolls? one would assume so as Rogues can UMD scrolls and have no spellclass type.

I think I have more but I'll leave them at that for now. As I said I'm just coming round to using scrolls and in all our previous games we've been a bit magic light and only had a wizard scribing his own spells which wasn't an issue.

First off do spells cast from Scrolls incur Arcane Spell Failure? As an arcane duelist I'm looking at ending up in full plate so probably won't bother until I've found a way round it.

Using a scroll works the same as casting the spell for purposes of arcane spell failure. So if ASF applies to the spell itself, it applies to the scroll.

Which brings me to, thirdly: Can I use UMD for divine scrolls? one would assume so as Rogues can UMD scrolls and have no spellclass type.

Yes. Use Magic Device allows any character to use any scroll if they succeed on the check.

Secondly (and I saw a thread on this that didn't seem to come to a conclusion): If I cast a scroll written by a wizard do I have to use INT for the prerequisite stat line and resultant DC? Obviously as it could have been scribed by a sorceror and found scrolls are only ever differentiated by arcane and divine and not by individual spellcaster.

Which brings me to, thirdly: Can I use UMD for divine scrolls? one would assume so as Rogues can UMD scrolls and have no spellclass type.

You will need to use UMD even for many arcane spells, specifically those not on the Bard list.

1. Yes, scrolls incur arcane spell failure as normal.

2. The DC is set by the scroll's caster. The ability score requirement is for the spell level (10 + spell level). You don't use your Int -- you use your Cha. For example, to cast a scroll of cure moderate wounds, you need a 12 Charisma. However, if the spell is not on your spell list, you have to apply the ability score used to create the scroll and therefore emulate that ability score as mentioned in UMD.

3. Yes, you can use UMD to cast divine scrolls.

The DC is not set by the scrolls caster - it is 10+spell level +the mod on the minimum stat to cast it. Neither your charisma nor their int enters into it.

Note the UMD doesn't let you overcome the caster level check, but that's what the bard levels are for. Rogues can't actually use scrolls.

"Using a scroll is like casting a spell for purposes of arcane spell failure chance."
So if it's a bard spell, you're fine, since you ignore spell failure for bard spells. If it isn't, then it might matter. Divine spells are fine though, as long as you make that UMD check.

The ability for the scroll apparently does depend on who scribed the scroll - you definitely want sorcerer scrolls if no bard, otherwise you are using UMD *again* for the int/wisdom requirements.
http://www.d20pfsrd.com/skills/use-magic-device.

The DC is not set by the scrolls caster - it is 10+spell level +the mod on the minimum stat to cast it. Neither your charisma nor their int enters into it.

Note the UMD doesn't let you overcome the caster level check, but that's what the bard levels are for. Rogues can't actually use scrolls.

This is correct about the setting the DC of a scroll. Your ability does not come into play, neither does that of the person who scribed the scroll.

For example, a scroll of Fireball scribed at caster level 5 would have a DC of 14 (10 + 3 for 3rd level spell + 1 for ability score of 13 to cast). Even if it was scribed by Elminster or Mordenkainen, the DC would be 14. Unless Heighten Spell or some other affect was applied at the time of scribing.

The part about rogues not being able to use scrolls is incorrect IF they have ranks in Use Magic Device which I think is what was being implied earlier. If so, a rogue or any class would just have to make a UMD check equalt to a DC of 20 + spell level (a DC 23 in the case of the scroll of Fireball). In this case the DC would still be 14 for the scroll of Fireball.

Use a Scroll: Normally, to cast a spell from a scroll, you must have the scroll's spell on your class spell list. Use Magic Device allows you to use a scroll as if you had a particular spell on your class spell list. The DC is equal to 20 + the caster level of the spell you are trying to cast from the scroll. In addition, casting a spell from a scroll requires a minimum score (10 + spell level) in the appropriate ability. If you don't have a sufficient score in that ability, you must emulate the ability score with a separate Use Magic Device check.

Emulate an Ability Score: To cast a spell from a scroll, you need a high score in the appropriate ability (Intelligence for wizard spells, Wisdom for divine spells, or Charisma for sorcerer or bard spells). Your effective ability score (appropriate to the class you're emulating when you try to cast the spell from the scroll) is your Use Magic Device check result minus 15. If you already have a high enough score in the appropriate ability, you don't need to make this check.

Example: Bard casting heal of a scroll.