After my mail order mango debacle in which I killed a few mango trees I went to a local nursery and was pleasantly surprised to see a selection of fruit trees. I bought a mango, a lychee and navel orange. My questions are...

1.) When to transplant them from the standard 3 gallon nursery pot to a bigger container?

2.) What size is best to upgrade from the 3 gallon pot? 5? 7?

3.) I'm assuming these aren't organic as they are littered with blue pellets so can I convert them to organic after transplanting?

4.) Is a bright sun room enough light till spring/summer?