>1) Does a 'resist heat' prep have an impact on fela's vuln to
>fire?

Yes. Normally you would take 4/3 the normal damage from fire. With resist heat you take 2/3 the normal damage, just like someone would who doesn't have a fire vuln. Having "resist heat" takes you all the way from "vuln" to "resistant".

>3) Is there any 'resist fire' prep in game?

Nope. Resist heat = resist fire.

>4c) Guess true question is : Is this prep really worthed to
>use?

Depends on how much you value the "limited resistance to all attacks". It's cheap and easily purchased, so it seems worth it to me. The down side is that it causes certain things to not show up in your affects list. You're still affected by them, you just can't *tell* that you're affected by them by using the "affects" command.