The usage of でも

Question

I am getting a bit confused with the multiple uses of でも. Permission, even if, without doing, etc.

I have the following 2 sentences to translate. Note - these sentences might not be valid

1. わからないでも言って下さい
   Please say it without understanding.

2. 二時間おきでもいいです
   Even every 3 hours is okay.

Are these sentences valid, and if so, are my translations correct?

Answer 1

There is two ways I can see for your first sentence. First you could write it:

わからない。でも、言って下さい

In this case you would separate it in two sentences meaning: "I don't understand. But say it"

In which case, it is the closest if I try to not change your japanese sentence. If I go the other way around by trying to not change your english translation, I find it better to say:

わからなくても言って下さい

On your second sentence, few changes ought to be made. If what you want to say in english is "Even every 3 hours is okay", I would rather say it this way in Japanese:

[毎三時間]{まいさんじかん}でもいいです。

Answer 2

Both of your sentences are invalid.