Its manifestations include the actual regenerate mechanic (found on older cards), as well as life-gain and the ability to regrow cards from the graveyard to hand
for the most part, its rules were the same as the tabletop version, and it was a decent way to learn how to play the game
You may not wait and cast it later in the turn (unless of course the ability triggers and resolves again).
Even with just Mikanko Ceremony and Curse, you can Ritual Summon from the deck using Curse as a cost, tribute the Mikanko Ritual Monster to self-revive Curse, and search for a Mikanko card, which technically works as a starter
If you have a stack of raw cards you want to move, this is a very efficient platform for it
Modern online trading card games are nearly always an online service, constantly updating with new mechanics to learn and cards to buy