From what I've heard, these tips only seem to be in the web version of Duolingo, not the mobile version. On the web version, when you select a skill, there will in some skills be a light bulb symbol next to the key symbol above the start button. Click on this light bulb to go to the tips and notes for the skill.
That would be Jag gillar denna/den här stad(en) eller Jag tycker om denna/den här stad(en). As there is a direct translation for like rather than love it would not really be appropriate to accept an alternative translation which means something similar but not the same.
I disagree. Jag tycker att "älskar" och "gillar" har mycket samma betydelser (och användningar) som på engelska. In fact, Swedes from my other language courses have said that if anything "älskar" is less used på svenska than "love" is in English... though that is obviously a matter of opinion. My perception living here so far is that the uses are much the same. Regardless, it seems silly in an language course to allow people to exchange similar but different words in a sentence.