You can buy another galaxy bud online and then you just pair them. Guide to put them to pairing mode is here

Here’s the navigation Volume keys: Up is up Down is down Power button: Enter key Solution: Navigate to “reboot system now” and if it doesn’t fix try to reset to factory default settings. And if it still don’t work then last resort is to flash a new operating system (only if old os is corrupt.) guide to flash is here (if you REALLY need it, also flashing ersaes all your data as well as factory data reset but you are getting a new os (if you’re not good at it I strongly reccomend to flash a stock ROM.)) Also flashing helps if the recovery screen is frozen or not functioning as intended (Again if you don’t need to flash and you can just get back on track with tw other options I strongly reccomend to follow these methods unless you know what you’re doing.)

If you have your iCloud account in it. Connect your iPad to your pc, and download iTunes (If You don't have app.) Then pick factory

Its easier to buy new motherboard than attempting to fix it

Yes you can if you can find all parts. Only thing that needs soldering is battery on to logic board. But you can find these iphones cheaper on ebay

Silly question… Yes it fits but you cannot use it because iphone 5s screen has difrent type screen pins(Because the Touch ID) but if oyu put 5c screen in it it maybe even work. Not worth it.

Maybe you bent the digitizer pin when you replaced the screen but when this hapened you have to buy new logic board. This was best I find iPhone 8 Plus Bare Logic Board

The Best I Could Find https://www.ebay.com/itm/Nintendo-used-new-2DS-XL-Motherboard-Main-board-Replacement-Repair-Part-OEM-/222809810390

(1) If You Can Go To Home Then Read My Advice. (2) Go To Home (3) Open Up Settings (4) Go To Phone Information (5) Click On Build Number Repeat Repeatedly (6) Open Developer Options (7) Find Option Demo Mode (8) Simply Turn It Off Update (02/27/2019): Then you can try “The Microsoft Lumia Way”. Hard reset your phune by recovery mode

No. Its bearly impossible. It requires so much microsoldering and custom rom wich makes cheaper and better option to buy ipod touch 6 generation that costs much less than all this effort you put to replace ram chip. Also its bearly impossible to find better ram chip and ipod touch 6 has 1 gb of ram. you can also move all your content from old device to new one. So i suggest buying ipod touch 6.