Risk Legacy

You win immediately when you are the first player to have 4 Red Stars. (Rulebook, page 8.)

You may buy Red Star tokens only at the very start of your turn by turning in four Resource cards per Red Star, and you may buy more than one if you have the cards. (Rulebook, page 8.)

No — you only draw a Resource card if you attacked and conquered at least one territory from an opponent; expanding into unoccupied territories (even with a city) does not qualify. (Rulebook, pages 10 and 12.)

Recruitment = (your territories + your population from cities) ÷ 3 (round down, minimum 3), plus any continent bonuses and troops from turning in Resource cards; city population is added to your territory count. (Rulebook, page 9.)

The attacker may commit up to 3 attacking troops (roll up to 3 dice) and the defender up to 2 troops (roll 1 or 2 dice); compare highest dice down, and the defender wins ties. (Rulebook, page 10.)

You control the HQ piece that remains on the board and thereby gain that Red Star (you do not take a Red Star token from the supply; Red Star tokens never change hands). If controlling that HQ gives you your fourth Red Star you win. (Rulebook, pages 8 and 12.)