Ok.. are you ready for our list of foods that our bettas get?

we have: freeze-dried bloodworms, frozen bloodworms, freeze-dried daphnia, vitamin pellets, betta pellets, color pellets, betta flakes, soft pellets with krill in them.. we also regularly feed them frozen peas, thawed and peeled.
Our feeding schedule for the bettas is that they get fed when we have breakfast and dinner (and they know it.

). each feeding, they get 3 pellets, bloodworms or the equivalent flakes or 3 pellet-sized pieces of the pea.
For breakfast: mon they get pea pieces, tues - friday they get vitamin pellets (except our finicky Sora), sat they get bloodworms.
For dinner: mon they get pea pieces, sat they get bloodworms and tues-friday we cycle through the other foods.
Sunday they get fasted. It's also good to give them a little time between pieces when feeding (it makes it a good time to talk to them and enjoy watching their food-antics). 1 piece at a time - to answer one of your questions.
Basically all of this is to aid in digestion and nutrition for them and prevent constipation. Only Sora is finicky and will only eat daphnia, bloodworms and peas, so he's on a different schedule, but we balance his diet with those 3 foods so that he doesn't get constipation.
The frozen bloodworms are thawed by putting them in a sealable container with room temp. distilled or treated tap water. The frozen peas are thawed with about 50 seconds in the microwave, then they're easy to peel and tear into little pieces. Bettas also like an occasional treat of fruit and it varies from betta to betta what fruit, but all of ours were happy with cantaloupe.
Some balk at worms (or other new foods) at first, some actually don't eat them.. they have unique characters and personalities so you can find all kinds of food likes/dislikes with them.