Yes, you can attach the phone lens to the main phone camera of iPhone 13. 

Yes you can. In fact that is what I am doing right now. The one that came with the telescope was alright but the camera tripod I have is a Polaroid and works much better. 

No this is a stand alone device, it does not require any other devices to work. It comes with a mini memory card that you can remove and put into a computer to add pictures to charts. That is the only way to get info off unless you snap a picture of the picture with your iphone which honestly is probably faster 

(1)Please check to make sure you have installed 1.5V 6*AA battery. Do not use inferior batteries as their voltage is lower than 1.5V. (We recommend brands like Energizer, Duracell, AmazonBasics, etc.). (2)Make sure the polarity is correct and the contact with the spring is normal. (3)Press and hold the power button for at least 3 seconds to power on. (4)If it still cannot be turned on after 1-3 steps, please try to use a power bank. 

The part for that use is extendable so can fit most phones but this part of the monocular is absolute rubbish. It scratches the phone and just doesn't work for that purpose at all. The actual monocular is very good though if you want to use it normally.