I want to use all six I/O pins of an ATtiny85, that means also using the reset pin as an I/O pin, however, I found out that if I disable the RESET pin, I can no longer program the ATtiny using an ISP programmer.
However, I found out that there are bootloaders for ATtiny which, as far as I understand, allow me to program the ATtiny through USB, without the need of the RESET pin.
My question is: How do I burn such a bootloader (such as micronucleus for example) to the ATtiny85? And how do I need to connect the ATtiny to USB after that (like this?)? How do I program it after that? Keep in mind that in terms of burning bootloaders and modifying fuses, I am a complete newbie.
Also, I'm using the ArduinoISP sketch as my ISP programmer since I don't have a real ISP programmer, but as far as I read, that won't be a problem.
EDIT: I do have this thing I bought for a couple dollars on eBay, which I don't know how and if I need to to use: