Normal ATX standard, only the maximum length has to be considered.

Unfortunately, I no longer have them.

Hi The fans of this enclosure are connected to a controller device and then controlled with a remote control. The controller device draws power via a Sata connection. With the power supply unit, just make sure that there are enough Sata connections, but by now every power supply unit has this :)

There is room for a 280 mm radiator at the top, but no radiator holder. If you are already using such expensive Aio, I would also switch to a high-quality housing from e.g. Corsair.

Yes, it is possible to install this watercooler in this case.

https://kolink.eu/onewebmedia/Cases/OBSERVATORY%20LITE/OBSERVATORY%20LITE.pdf

The fans, which are installed as standard, cannot be purchased, as far as I know.

No, I had to install a Kraken x53. Fans of the size 140mm cannot be installed in the case. I have the Kraken x53 with a 120mm fan and am totally thrilled.

Several different screws are included. Metric as well as self-tapping screws

Because of just one more milimetre, it should probably be OK

Yes.

Which 3060 TI do you want to install? This case has a length of 335 mm (max. length graphics card 335 mm), the 3060TI already exists from 233 mm (MSI DUAL FAN).

Not as it looks. This case does not have vertical GPU brackets.

Yes: "The four pre-installed 120 fans with digitally addressable RGB LEDs can be controlled via the supplied RGB hub and the accompanying remote control. Alternatively, the fans can be connected and controlled via a compatible motherboard as the fans have a standard 3-pin 5VDG connector." See image: https://kolink.eu/____impro/1/onewebmedia/Cases/OBSERVATORY%20LITE/GEKL_065_09.jpg?etag=%221b47b-5efc3554%22&sourceContentType=image%2Fjpeg&quality=85

https://kolink.eu/onewebmedia/Cases/OBSERVATORY%20LITE/OBSERVATORY%20LITE.pdf