I've got a question - what's the difference between "idag" and "i dag"? Thanks in advance for the answers!
It has become the most common practice to write i dag/i morgon/i kväll etc as one word during the last decades. I do so, in all kinds of text. Very often (in sms/chat) I abbreviate "imorgon" into "imorn" (since i would pronounce it like that). Many people even write "imon".
In English, one usually says, "Is today Friday?" Can this be an acceptable translation as well?
In some languages weekdays are capitalised, in some they're not. I don't think there's any special rule behind it.
For some reason (historical reasons) you seem to consider these words to be names ('proper nouns') in English, but in Swedish, we don't. Most other languages don't either. Some languages, notably German, capitalize all nouns. Basically it's a question of spelling conventions, in many cases decisions that were made way back in history.
Etymologically, the days of the week are derived from names—mainly those of the Norse gods, so I can see why English would have opted to capitalize them.
The word order is different. In a statement, we'd say Det är fredag i dag (with the verb in the second place). But since this is a question, the verb needs to go before the subject, so we ask Är det fredag i dag?
In the recorded speech, the first g is pronounced but the second isn't: "fredaG i dag." Is that because it's followed by "i" ? like the liason in french? Or is it bad speech?
You can say it either way. The g in fredag tends to be heard at least whenever one tries to speak a little extra clearly. It usually isn't heard in normal casual speech, but there's absolutely nothing wrong with pronouncing it either. It's not really like a liaison but it's probably more likely to be heard before a vowel than before a consonant.
PS the g is always heard in forms like fredagarna where there's a vowel after in the same word (unless we swallow the entire following syllable and pronounce fredagen as fredan, which is very common in some words), but in compound words starting with fredags- it usually isn't heard. So to some extent it does matter whether there's a consonant sound after it or not.
Subtle difference, but that's asking when Friday is rather than whether a certain day is Friday.
Is the 'g' in 'dag' here meant to be so silent or are my speakers behind weird?
Just to confirm, it's usually silent in general or only at the end of a sentence?
In general, though the probability that it will be pronounced increases if the next word starts with a vowel sound.
it's cruel to give me this sentence on a monday morning when i'm on my way to school