What's your question? Ask

Deciding when to harvest peaches is a matter of personal preference. While most people prefer tree-ripened fruit, but fruit at this stage has an extremely short shelf life. Therefore, it may be better to pick the fruit two to four days before it is fully ripe. Here are some things to look for when harvesting peaches: When the fruit is easily pulled off the twigs then it is probably ripe. You should feel a certain amount of movement when you press in to the flesh of the peach with your fingers. When peaches change from green to an orange tint, they are nearly ripe. Ripe peaches will give off a pleasant, peachy smell.

Here is a link that address common Peach tree diseases and methods of treatment.

https://www.gardeningknowhow.com/edible/fruits/peach/common-peach-diseases.htm

There are Zone 4 cultivators of peach trees.

A peach tree would not be a suitable indoor tree.

https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-care.htm

They peach tree was likely a grafted tree and the root stock is from another tree of some kind.
The root growth likely would not be a Peach tree variety. It is best to dig up and remove and start a new tree.

I'm sorry your tree was lost.

Look up bonsai on the web it should answer your question

Here are a few links for you with more information.

https://www.gardeningknowhow.com/edible/fruits/peach/fertilizing-peach-trees.htm
https://www.gardeningknowhow.com/edible/fruits/fegen/reasons-for-small-hard-fruit.htm