Both are correct. There are some verbs in Greek called "συνηρημένα ρήματα" (contracted verbs) that have two ways of telling them. Verbs that end in -αω (such as αγαπάω) fall in this category. Εγώ αγαπάω/αγαπώ, εσυ αγαπάς, αυτός αγαπάει/αγαπά, εμείς αγαπάμε/αγαπούμε, εσείς αγαπάτε, αυτοί αγαπάν(ε)/αγαπούν(ε)
Do you have the Greek keyboard? If not see here: HOW TO GET THE GREEK KEYBOARD https://forum.duolingo.com/comment/17486118
These links will not only show you how to get the Greek keyboard but also how to find the Greek letters on it, how to add accents etc.
η, ο, το are the articles for the words that are grammatically feminine (η), masculine(ο), neuter (το). To learn more read the Tips & notes for the earlier Skills...Basic 1 etc.
Some simple hints to get you started:
1 Always read the comments before posting.
2 Read the Tips & notes, on the first page of each lesson you’ll see TIPS. Click on that. 3. Read the drop down hints. Pass your cursor over a word and a list of words will appear. The top word/phrase is usually the best choice. Or go to the top of the page and click MORE you’ll see a dictionary; just type the word.
4 Use the Report options at the foot of the exercise page to Report issues such as **My answer should be accepted.” etc Then be sure to leave a comment on the Discuss Forum
Unlikely, as the first form is used for the subject and the latter for the object. You can have an object-verb-object structure in Greek, but a sentence where you use ο άντρας is not going to have the same meaning with one that uses τον άντρα, so it can't have been the same sentence.