Time Will Tell - Turn Figures into Information

English usually deals with the minutes first, then the hours (not like most of the Romance languages). Answer 3 is more or less word-for-word from the Russian; Answer 1 is certainly possible, but English people (on the whole) don't seem very comfortable with the 24-hour clock. We do tend to accept it when talking about international travel ('arrive Heathrow 20:45'), but not for most everyday conversation.

Two quite simple English words will 'bracket' the start and stop times (or dates) of almost anything, whether it's a business meeting or the length of time that Queen Victoria reigned (64 years), or even some far distant period of archaeology.

These are both 'figurative expressions' (they may have numbers in them, but they're not meant literally). Some of the 'distractor' answers may have tempted you if you are a native speaker of French or Hebrew. Different languages, and their speaker communities, tend to use different numbers to express these ideas!

This is short for 'in 20 minutes' time' (or even 'within ...'); then we do one thing before another.

We set a deadline 'in [so much] ... time from now'. 'After' (Answer 3) is also possible, but less likely.

We say 'at' any whole hour, or indeed any time at all ('at noon'; 'at a quarter to six'; 'at three o'clock').

'For how long' and 'since when' are the ways we use to explain how long something has been going on. You may well wish to tell people how long you have been learning English, or how long you have practised some other activity that is important to you.
Note that in English, we use a Past Continuous tense in these circumstances; in your own language (certainly most European ones), the structure is much simpler because you say, in effect 'I do this since then' (or 'I am doing ...') - using your Present Tense, because it's still true. English is a little more subtle, and deep, in terms of suggesting the passage of past time. It isn't particularly difficult, but you need to remember that it works differently from what you may be used to!

English always says 'on ... [a particular day]', even when there is no physical sense of being 'on' it (like 'on a boat, on the English Channel' or whatever). But we do say 'at' the weekend, or sometimes 'over' or 'during' the weekend, each of which suggest - quite rightly - that a weekend is longer than one single day.

'At' a time, 'on' a date ... remember! And a very Happy Christmas to you, next time it really comes round!

'Every other' is rather a neat phrase meaning 'every second / alternate' week: in this case, if they did that collection last week, they will miss it out again and come next week; or if they did it this week, they won't be coming again until the week after next.
'Every other' ordinary number would either be all the odd numbers, or all the evens, but not the ones in between in either case.
German has a neat word 'anderthalb' which means one-and-a-half of something, such as that one mile is about one and a half kilometres. As ever, different languages have their own ways of dealing with these ideas!