Visit the link and create an account. This link doesn't expire. Play to earn apps/ websites usually have a native token (they might have ongoing and upcoming airdrops [or airdrops of tokens which are already existing]). They might have a staking feature.
The code is entered upon registration. The code doesn't expire. Get paid to sell unused bandwidth or computing power, this is done in the background while you're doing other things, earnings are calculated based on your PC's or Mac's processing power and luck. If you want to earn more from these kind of apps purchase extra devices, hardware or components. Before you can purchase a hardware, service or device calculate your returns.