It could be either, it’s hard to say for certain. Was it working fine previously? If so, the battery seems to be fine unless it was left out for ages, depleting the battery to the point where you have to charge it for a while for anything to happen. It could also just be the charger as if it is not going on charge or recognising that it should be charging then that may be your issue. I would say the charger is more likely and one to start with but if still nothing, then definitely battery.
In my honest opinion I can’t say it’s salvageable unless you know of someone who deals in micro soldering repairs. By the sounds of things, the coffee and the fact that you used water, even if it’s distilled, means you’ve caused corrosion on the components within your motherboard and they are either damaged or short circuited. This will prevent it from turning on. If you want to learn micro soldering and have some tools, Louis Rossmann on YouTube is a good start, but if not, you will have to send it away for diagnostics or repair or it’ll go in the bin if there’s no warranty / coverage. Sorry.
You could try and fit a new battery first to rule that out, seeing as it would be the cheaper option. This is because most likely unless you’re great at multi-pin desoldering, you’re gonna have to replace the entire motherboard / pcb. But for £24.24 ($31.25) you can buy a new / used board that’s been dismantled from a previous 3DS. https://www.aliexpress.com/item/Original-US-Version-Main-Logic-Board-Motherboard-for-Nintendo-3DS-Repair-Parts/32913355306.html?spm=2114.search01...-c715-408a-8109-a2782846e1d3-11&algo_pvid=995c5205-c715-408a-8109-a2782846e1d3&priceBeautifyAB=0
I’m not sure if that would work. Yeah the motherboards may be same but they will have entirely new IC’s on board and apparently the rear camera has a dedicated chip for camera adjustment and zoom levels etc. Therefore, if you upgraded, the connectors on the camera will most likely be different and will not have the IC needed in order for the camera to function correctly. Why not just get an upgrade / contract or pay the pro off on finance and pay for a SIM only deal?
You could try to factory reset the device to see if it’s a software issue. If that doesn’t do anything, then my best guess if that your LCD back light has gone bad and that you may have to replace the entire LCD assembly. You can purchase a replacement LCD here for around £120: https://www.aliexpress.com/item/Original-6-inches-HD-Eink-Screen-for-kindle-oasis-2016-eBook-Reader-LCD-Display/32867192348.html?spm=2114.search...-9be9-4538-bd11-d15047a6f119-0&algo_pvid=22493d07-9be9-4538-bd11-d15047a6f119&priceBeautifyAB=0 The only other option could be, take it apart, remove the screen and put it back and ensure that the connector on the ribbon cable is clean and seated correctly. The cable may have become positioned wrong from being knocked or dropped.
It’s possible that if you haven’t created partitions that some Windows files have been either over written or corrupted. Wipe the drive clean, partition it for each OS then install them again to the relevant partitions.
Only thing that would come to mind for me is the fact that ‘kernel’ is memory associated. However I dug around and found this quoted on another site. ‘Use Run and type regedit HKEYLOCALMACHINE > SYSTEM > Currentcontrolset > control > graphicsdrivers. Right click graphicsdrivers, click new >Dword (32-bit) value. Modify the value to 8 What I did next was delete ALL of my graphic driver installed (the nvidia one). It will swap to the build-in one on your motherboard. Then use driver sweeper, select nvidia, and let it erase ALL of your nvidia driver files. I then re-installed the nvidia driver through the installation CD I got with the graphic card, and did NOT get any updates.’
Try shining a flashlight at the TV (get close up) and see if you can see a faint display, if you can then your backlight LED’s have gone bad and you have to take your whole TV apart to get to them. Cheap repair in some cases (model dependant).
What do you mean by boot loop? Does the laptop power on, show the logo and just repeat? If so, that may be to do with the hard drive or a problem with the BIOS. I had a similar problem before, I believe my issue was a dodgy hard drive and had to chuck it and put in a new one. Try swapping a hard drive for a new or different one.