In your end step, you put a +1/+1 counter on each dork and you untap them too
Number 169 Language English Legal Formats Brawl, Commander, Competitive Brawl, Legacy, Timeless, Vintage Not Legal Formats Alchemy, Pauper, Standard Banned Formats Historic, Modern, Pioneer Rulings (10/4/2019) The earliest opportunity you have to cast Once Upon a Time is during the first player's upkeep, before that player can play a land.
Also, it can be small, and then it transforms back
Always insist on a public, safe location for in-person trades and verify the cards authenticity (use a grading companys database!) before finalizing the sale
Basically, the conventional wisdom in Modern is that you can play up to three colors relatively smoothly with a fetchland-powered manabase