French language Q&A Forum

When do you use quand and when do you use lorsque?

I recently saw a rule that confuses me regarding qualitative adjectives. It says absolute qualities should not be modified by additional adjectives if they are comparative or superlative.

One example was "delicieux", it is an absolute quality and one should not say "c'est tres delicieux". To me, this makes no sense. If true, many people break the rule. Plus, I don't consider "tres" a comparative or superlative. Some of the other examples given were "éternel, parfait & admirable". I did a lot of searching and can find no other references, but I may be missing a magic keyword. I would ignore it except that the source is usually good and it was in the context of "very common French errors"

The rule does seem to make sense with some adjectives, from an English perspective. One would not say something is "very eternal", it's either eternal or it's not. I don't see delicious the same way.

Am I misunderstanding this? Can someone clarify? 

This is a sample sentence from this lesson: 

J'ai de plus en plus de mal à me concentrer.

I understand the more and more part.  As a student, without the translation, I would not have come up with I'm struggling more and more to focus.   I was seeing this as ... I have (more and more) pain myself to concentrate.  Is there a lesson on avoir mal a that talks about struggling?  If so J'ai de plus en plus de mal avec cette example! :)

If a bag (sac) is described as heavy wouldn't it be lourd not lourde as sac is masculine?

J'ai visité Versailles dimanche dernier.

Why is it not: le dimanche dernier?

Checking whether these words are interchangeable, or whether there are nuances we should know about:

Parfois vs quelquefois 

mare vs. étang vs bassin 

morceaux de tomate vs pièces de tomate

Thanks!

Why can’t we use on traverserait de la Guadeloupe.... in stead of on passer de la Guadeloupe?

"Enfin, les amateurs d'histoire apprécieront le Vieux Bordeaux"

I thought enfin was used when an expected result occurs (foreseeable outcome) and finalement was used for an unexpected result (unforeseeable outcome).  Is there a better way to keep these two words straight? In the above sentence, how would a visitor to Bordeaux know what to expect before actually seeing the city?